Here - Warilla High School Intranet

Transcription

175P IPT HSC Cover
7/9/00
9:23 AM
Page 1
Key features
• list of outcomes and overview at the beginning of
each chapter
• social and ethical issues and Internet activities integrated
throughout the book
• numerous practical tasks that can be used with any
software or make of computer
• case studies and examples of information systems
• learning activities to help students apply the content in
every section
• chapter review at the end of each chapter
• interesting IT facts and cartoons 1to2promote
3 4 5class
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• key terms highlighted for quick reference
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• glossary
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• index.
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Additional resources to support and
are0 - 1 2 3 4
1 2extend
3 4 5this
6 book
789
available at Heinemann’s World Wide Web site, hi.com.au.
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These include a sample teaching program, assessment
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advice and answers to exercises from AtheS textbook.
About the author
Greg Powers is a head teacher with many years’ experience
in writing and implementing computing studies programs.
He is the author of several highly successful texts including
Computing Studies–An Introductory Course.
ISBN 0 86462 501 4
ISBN 0-86462-512-X
You can visit the Heinemann World Wide Web site at
hi.com.au or send email to info@hi.com.au
9 780864 625120
G.K. Powers
Also available
Heinemann Information Processes and Technology:
Preliminary Course
Heinemann Information Processes and Technology: HSC Course
HSC Course has been written to meet all of the
requirements of the new Information Processes and
Technology syllabus in NSW. This text will help students to
develop their understanding of information processes in the
context of different information systems. It is designed to
build on the knowledge and skills gained in the Preliminary
course and to help students become confident, competent,
discriminating and ethical users of information technology.
This text provides up-to-date information, a practical
approach, and a large number of questions that cater for a
wide range of students.
H e i n e m a n n
Information Processes
and Technology
1234567890-1234567890-1234567890QWERTYUYIOPQWERTYUYIOPQWERTYUYIOP
HSC COURSE
!@ $%^&*()_)_+!@ $%^&*()_)_+
!@ $%^&*()_)_+!@ $%^&*()_)_+
G. K. Powers
Y
F
Y
F
Heinemann
and Technology
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1234567890-1234567890-1234
QWERTYUYIOPQWERTYUYIOPQWERTY
HSC COURSE
ASDFGHJKL:”ASDFGHJKL:”ASDF
ZXCVBNM<>?ZXCVBNM<>?ZXC
!@ $%^&*()_)_+!@ $%^
1234567890-1234567890-1234
QWERTYUYIOPQWERTYUYIOPQWERTY
ASDFGHJKL:”ASDFGHJKL:”ASDF
ZXCVBNM<>?ZXCVBNM<>?ZXC
!@ $%^&*()_)_+!@ $%^
G.K. Powers
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Heinemann
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2003 2002 2001 2000
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cataloguing-in-publication data:
Powers, G.K. (Gregory K.).
Heinemann information processes and technology :
HSC course.
Includes index.
ISBN 0 86462 512 X.
1. Information storage and retrieval systems. 2. Electronic
data processing. 3. Information technology. I. Title
004
Disclaimer
All the Internet addresses (URLs) given in this book were valid at the time of
printing. However, due to the dynamic nature of the Internet, some addresses may
have changed, or sites may have ceased to exist since publication. While the authors
and publisher regret any inconvenience this may cause readers, no responsibility
for any such changes can be accepted by either the authors or the publisher.
Contents
To the teacher
About the contributing authors
Part 1 Core
v
vi
1
Chapter 1 Project work
1.1 Project management
1.2 Social and ethical design
1.3 Understanding the problem
1.4 Making decisions
1.5 Designing solutions
1.6 Implementing
1.7 Testing, evaluating and maintaining
Chapter review
2
4
8
12
15
18
26
29
33
Chapter 2 Information systems and databases
2.1 Information systems
2.2 Organisation methods
2.3 Storage and retrieval
2.4 Other information processes
2.5 Issues related to information systems and databases
Chapter review
35
36
42
53
64
69
73
Chapter 3 Communication systems
3.1 Characteristics of communication systems
3.2 Examples of communication systems
3.3 Transmitting and receiving
3.5 Issues related to communication systems
Chapter review
75
76
80
87
100
104
109
Part 2 Options
111
Chapter 4 Transaction processing systems
Christopher Lean
4.1 Characteristics of transaction processing systems
4.2 Examples of transaction processing systems
4.3 Storing and retrieving
4.5 Issues related to transaction processing systems
Chapter review
112
113
119
126
134
139
144
iii
Chapter 5 Decision support systems
5.1 Characteristics of decision support systems
5.2 Examples of decision support systems
5.3 Organising and decision support systems
5.4 Processing and decision support systems
5.5 Analysing and decision support systems
5.7 Issues related to decision support systems
Chapter review
Quentin Evans
146
147
152
159
167
171
176
179
184
Chapter 6 Automated manufacturing systems
Wayne Moore
6.1 Characteristics of automated manufacturing systems
6.2 Examples of automated manufacturing systems
6.3 Collecting in automated manufacturing systems
6.5 Issues related to automated manufacturing systems
Chapter review
186
187
192
198
207
213
217
Chapter 7 Multimedia systems
7.1 Characteristics of multimedia systems
7.2 Examples of multimedia systems
7.3 Displaying in multimedia systems
7.5 Issues related to multimedia systems
Chapter review
219
220
230
238
245
254
258
Glossary
Index
Acknowledgments
Ellen Sheerin
260
268
274
To the teacher
This book has been written as a textbook for the New South Wales Information
Processes and Technology HSC course. The aim of this course is to enable students
to become confident, competent, discriminating and ethical users of information
technologies and information processes. This book addresses this aim and provides
an excellent understanding of all aspects of information technology.
Even though students undertaking this course have satisfactorily completed the
Preliminary course, they will vary substantially in understanding and skills. This
book has been written to cater for students with a wide range of knowledge levels.
Organisation of the text
The book closely follows the syllabus and the software/course specifications. It is
presented in two parts. Part 1 covers the first three components of the syllabus
(60%). Each component occupies 20% of the course time. Part 2 covers the option
strands (40%). Students are required to select two options. Each option covers
20% of the course time.
• Part 1 Core
1 Project work (20%)
2 Information systems and databases (20%)
3 Communication systems (20%)
• Part 2 Options (Students select only two options)
4 Option 1: Transaction processing systems (20%)
5 Option 2: Decision support systems (20%)
6 Option 3: Automated manufacturing systems (20%)
7 Option 4: Multimedia systems (20%)
Teaching program
Teachers can decide on the sequencing of the content depending on the ability
and knowledge of their students. The first chapter on project work is fundamental
to the other chapters. Students need to cover this chapter early in the teaching
program. Projects can be one large project or a number of smaller projects. Project
work in the HSC course is intended to give students an opportunity to plan,
design and implement an information system. The information systems chosen
should be one of the following:
• a database information system
• a communication system
• a transaction processing system
• a decision support system
• an automated manufacturing system
• a multimedia system.
The teaching program needs be consistent with the indicative times specified
above.
Additional resources to support and extend this book are available at the
Heinemann World Wide Web site (hi.com.au).
v
About the contributing authors
Christopher Lean is a programmer who develops and publishes software for his
company InfoVision. He has taught at TAFE level and at UTS and UNSW, and has
worked with a range of industries as a consultant.
Quentin Evans is an experienced teacher of Science and Computing Studies,
having taught a variety of computer courses since 1986. She currently holds the
position of Computer Coordinator at Concord High School.
Dr Wayne Moore is a senior lecturer in computing at Charles Sturt University,
Bathurst. He has been a mathematics teacher and science lecturer and currently
teaches information technology to undergraduate and postgraduate students. He
conducts research in industrial control systems and robotics and has interests in
simulation and virtual worlds.
Ellen Sheerin has been involved in teaching computing courses in schools since
1985 and is currently Computer Coordinator at Gorokan High School. She has
been an HSC Computing Studies examination marker as well as presenting
workshops in computing for teachers.
vi
Core
Chapter 1
Project work
Chapter 2
Information systems and databases
Chapter 3
Communication systems
1
chapter
PROJECT WORK
Outcomes
Overview
Project work for the HSC course follows the five
stages of the traditional system development
cycle that were outlined in the Preliminary
course. This chapter builds on these concepts
and includes additional content on prototyping
and participant development. Students are
required to construct an information system
using the knowledge gained from this chapter.
• applies an understanding of the nature and
function of information technologies to a
specific practical situation (H1.1)
• explains and justifies the way in which
information systems relate to information
processes in a specific context (H1.2)
• analyses and describes a system in terms of
the information processes involved (H2.1)
• develops solutions for an identified need
which address all of the information processes (H2.2)
• evaluates the effect of information systems
on the individual, society and the environment (H3.1)
• demonstrates ethical practice in the use
of information systems, technologies and
processes (H3.2)
• proposes ways in which information systems
will meet emerging needs (H4.1)
• justifies the selection and use of appropriate
resources and tools to effectively develop and
manage projects (H5.1)
• assesses the ethical implications of selecting
and using specific resources and tools (H5.2)
• analyses situations, identifies a need and
develops solutions (H6.1)
• selects and applies a methodical approach to
planning, designing or implementing a
solution (H6.2)
• implements effective management techniques (H7.1)
• uses methods to thoroughly document the
development of individual and/or group
projects (H7.2)
In the Preliminary course, you were introduced to the system development cycle.
It is a series of stages used in the development of a new information system.
The traditional system development cycle has five broad stages (see Figure 1.1):
1 understanding the problem—requirements of a system to solve the problem
2 making decisions—feasibility of a new system to solve the problem
3 designing solutions—creating the new system
4 implementing—using the system to solve the problem
5 testing, evaluating and maintaining—ongoing operation of the system.
In the system development cycle, there
are four important features:
• Each stage in the cycle is not always
separate and distinct. People involved
in the development of a new system
often switch between stages.
• The cycle does not end with the
testing, evaluating and maintaining
stage. It is a cycle, and the results
from the final stage are used for the
initial stages of another new system.
In this way the cycle is an ongoing
process.
• The extent of the cycle depends on
the complexity and size of the
project. In a small project, some of
the stages can be simplified and
completed very quickly. However, in
a large project, all the stages are more
involved. A large project usually
requires a detailed study of the
existing system and extensive work
in the analysis and design stages.
• Each stage of the system
development cycle has certain tasks
to be completed. It builds on the
conclusions of the previous stages.
However, there is often a good
reason to revisit the previous stages.
Understanding
the
problem
Statement of problem
Change
in purpose
Making
decisions
Type of new system
Change type
of system
Designing
solutions
New system
Change
system
Implementing
Using new system
Change use
of system
Testing,
evaluating
and maintaining
Problem with system
Figure 1.1 Stages of the system development cycle.
Project work
3
1.1 Project management
Project management is the process of planning, scheduling and controlling all the
activities within each stage of the system development cycle. It aims to deliver a
new system within an acceptable time frame and budget. Project management
involves creating a project plan.
Project plans
A project plan is a summary of a project that specifies who, what, how and when.
It clarifies what needs to be done and helps people to understand how they fit into
the project. A project plan usually breaks the project into major tasks called
subprojects. It must provide an overall schedule, the details of the subprojects and
a schedule for each subproject. It must also identify the people, information
technology and data/information required by the system.
A project plan is an important tool that helps to deliver a system on time and
to minimise the effect of unanticipated problems. If a project has problems, they
can cause the schedule to be lengthened and costs to be increased. They could also
force the project to be reduced in scope, and this could affect the success of the
project. To minimise problems, people working on the project should understand
the need for project goals, deliverables and schedules:
• Project goal—result of the project if it is successful. Goals may be broad, such
as creating a new system that works efficiently; or they may be very specific,
such as developing a system within a budget of $150 000.
• Deliverable—a tangible item expected from a task. It may be a diagram, report,
data dictionary, program or training manual.
• Schedule—the timing of major tasks and who will do the work. The success of
a new system depends on accurate time estimates for each task. A schedule
that doesn’t allow a reasonable amount of time for each task can actually result
in delays and additional costs.
ITITFact
Fact
Researchers have found that 37% of software faults would have been
avoided by appropriate scheduling and reducing the stress on developers.
Project plans are constructed and managed using information management
software and project management software:
• Information management software helps individuals on a project to manage
information and schedule tasks. It allows email messages to be exchanged and
organised. Appointments, events and meetings can be put onto an electronic
calendar and viewed by the day, week or month. Information management
software stores names and addresses of individuals and organisations.Tasks in the
project are assigned, sorted and organised. The progress made on tasks is seen at
a glance.
• Project management software contains most of the features of information
management software. It is a tool to efficiently plan, manage and communicate
information about a large project (see Figure 1.2). Project management software allows projects to be joined, tasks to be split among team members and
the project to be tracked over the Internet or via email. It provides analysis
tools to assist with decision-making, such as ‘what if’ analysis.
4
Core
Figure 1.2 Microsoft Project is an example of project management software.
One popular project management tool used to record and track schedules is
called a Gantt chart. A Gantt chart is a bar chart with each bar representing a task
or stage in the system development cycle. The vertical axis of a Gantt chart lists
the tasks, and the horizontal axis shows the time frame (see Figure 1.3). Gantt
charts provide a quick method of determining whether the project is on schedule.
They are used in meetings to review progress and identify problems.
Project plan
Evaluate existing
system
Data collection
Prototype
Proposal—new
system
1
2
3
4
5
6
7
Time (Days)
8
9
10
11
Figure 1.3 Gantt charts help to record and track schedules.
Project work
5
Communication skills
Communication skills incorporate a variety of strategies and techniques for
dealing with other people. Good communication facilitates the sharing of
information and genuine understanding. Some of the strategies for effective
communication are:
• Active listening involves restating, reflecting and summarising the speaker’s
major ideas and feelings. Active listeners encourage the speaker and are noncommittal.
• Conflict resolution solves arguments and disputes. It involves listening to the
other person’s views and looking at the conflict as a problem to be solved.
• Negotiation skills involve discussing a problem and arriving at a consensus.
They involve listening to different views and compromising to reach a solution.
• Interview techniques involve careful preparation, implementation and followup. A list of questions should be prepared with a clear purpose. Here are some
general rules for interviews:
– Make the interviewee aware of the purpose of the interview.
– Ask open-ended questions so that the interviewee must provide information.
– Check the responses by restating the interviewee’s viewpoint.
– Try to be aware of the interviewee’s body language. It may be communicating a different attitude.
– Close the interview by reviewing the main points and thanking the
interviewee.
– Review notes immediately and follow up with the interviewee on any
information that is unclear.
• Team building is the process of getting a group of people working together.
Each team member negotiates a role in the team with specific responsibilities.
The team members’ efforts are coordinated to ensure the efficiency of the
team.
Communication skills are required by every person in the project. The number
of people involved in a project depends on its size and complexity. It includes
information system personnel such as systems analysts and programmers. Systems
analysts perform the analysis to decide whether a new or updated system will
solve the problem. They must be familiar with the organisation’s operations and
the latest developments in information technology and computer programming
techniques. Systems analysts communicate their results to the programmers (see
Figure 1.4). Programmers convert a written description of a problem into a set of
programs. They code programs and produce documentation. Both systems analysts
and programmers work in teams and must be people with excellent communication and interpersonal skills.
A large project may involve hundreds or even thousands of people. To manage
the project, the organisation forms a project team and assigns the team to the
project. The team is responsible for the project from the beginning to the end. The
project team consists of participants, systems analysts and programmers. One
person from the team is appointed the project leader. It is usually a systems
analyst. A project leader (also called a project manager) develops schedules,
checks work and resolves conflicts. He or she ensures that the project is meeting
its goals. The project leader is responsible both for developing the project plan and
ensuring it is implemented correctly.
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Figure 1.4 Systems analyst communicating with programmers.
Exercise 1.1
1 List the five stages in the system development cycle.
2 Why is the system development cycle an ongoing process?
3 How does the system development cycle differ between a small and large
project?
4 What is a project plan?
5 Explain the difference between a deliverable and a schedule.
6 What is the purpose of information management software?
7 Why are Gantt charts a popular management tool?
8 List five strategies for effective communication.
9 Describe the role of a systems analyst.
10 What tasks are performed by a project leader?
LEARNING ACTIVITIES
1 ‘If each stage of the system development cycle is carried out properly, it should not
be necessary to return to the previous stage.’ Discuss this statement.
2 Describe one possible problem that might occur if the system development cycle is
not applied.
3 After one year of operation, an organisation had complaints from every department about a new information system. The new system contained a substantial
number of errors. At what stage of the system development cycle is it easier and
less expensive to identify and solve problems? Why? At what stage of the system
development cycle is it difficult and more expensive to identify and solve problems? Why?
4 Why is it important to be able to return to the previous stage when developing a
new system?
5 A project leader estimated a time schedule for the following tasks:
– Write system design documentation: 2 weeks
– Purchase application software: 1 week (during the system design documentation)
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– Code and test the custom software: 5 weeks (after the system design
documentation)
– Write hardware specifications: 1 week (after the system design documentation)
– Obtain quotations for hardware: 2 weeks (after hardware specifications)
– Select supplier of hardware: 1 week
– Deliver hardware: 2 weeks
– Install hardware: 1 week
– Set up software: 2 weeks (after hardware is installed).
Draw a Gantt chart for the project. What is the minimum time for completion of
the project?
6 A systems analyst has estimated the following time for these tasks:
– Define and code input screens: 5 days
– Define and code output screens: 3 days
– Define data structure: 2 days
– Define file structure: 4 days.
Draw a Gantt chart for the project if the tasks do not overlap. What is the
minimum time for completion of the project?
1.2 Social and ethical design
This section builds on the social and ethical issues discussed in the Preliminary
course. It examines the issues related to the implementation of a new system.
Design of systems
Information systems should be designed to take into account the strengths and
weaknesses of both people and machines. People are good at understanding and
thinking up new ideas but have an unpredictable memory and get bored with very
structured tasks. On the other hand, machines are good at repetitive tasks involving endurance, consistency and speed. They have very predictable storage and
retrieval times and can only perform structured tasks. The information processes
in a system should exploit the strengths and avoid the weaknesses of people
and machines. Machine-centred systems and human-centred systems provide
examples of contrasting designs.
Machine-centred systems are designed to simplify what the computer must
do at the expense of participants. They assume people will follow confusing
procedures and illogical user manuals. If errors occur in a machine-centred system,
they are usually blamed on the participant (operator error) rather than on the
technology. Machine-centred systems are not always the best systems for
participants.
Human-centred systems are those that make participants’ work as effective
and satisfying as possible. They allow people to do their work without wasting
time and effort struggling with the information technology.
In the past, information systems were difficult to use. People needed to understand a programming language to complete the simplest tasks. Today, with developments in technology such as graphical user interfaces, computers are much
more user-friendly.
User-friendly describes a tool that people find easy to use. User-friendly
information systems are more productive as participants do not waste time and
effort dealing with the system. In other words, the information system does not
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get in the way of the work. The software in the information system is a critical
factor in designing a user-friendly information system. It is the link between
people and the machines. User-friendly software has the following characteristics:
• prompts the user in non-technical terms (see Figure 1.5)
• doesn’t require precise spelling of commands
• uses a similar appearance and structure for multiple applications
• provides easier ways of achieving a task, such as templates
• structures menus so they are logical and easy to understand
• adjusts software to the ability of the user so that, for example, beginners see
and use only basic features
• allows previous work to be imported and used easily.
Figure 1.5 Wizards are a user-friendly feature.
Work environment
The design of a system impacts on the work environment. The impact can be
positive or negative. That is, for some people a new system can be exciting and
enjoyable while for others it is frustrating and difficult. When designing a new
system, it is important to consider the health and safety issues and the nature
of the work.
Health and safety
The relationship between people and their work environment is called ergonomics. It refers to the process of designing or arranging workplaces, products and
systems so that they fit the people who use them. The way information technology is used in the work environment can have an effect on the body. Incorrect
use of computers can cause health problems, such as eyestrain, headaches,
backaches, fatigue, muscle pain and repetitive strain injury (RSI). To reduce these
health problems, numerous reports and standards have been developed that deal
with ergonomics and information technology. The recommendations are briefly
outlined below:
• Furniture. Furniture needs to be adjusted to suit each person’s body. The desk
and chair should be positioned to reduce strain and undue fatigue. Desk height
must be between 660 mm and 680 mm. Chairs should have an adjustable seat
height that ranges from 370 to 520 mm. The seat should be flat, well padded
and slanted slightly backwards.
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• Information technology. The screen should be about an arm’s length away with
the user looking down on the screen. The keyboard must be detachable and
positioned so that the user’s forearms are parallel to the floor. The mouse must
fit the hand and be easily moved. Software must be ergonomically designed to
make the user feel relaxed and comfortable. It should minimise movement,
improve speed and be easy to use.
• Environmental factors. Lighting needs to be uniform and bright enough for
all text to be easily read. The air temperature should range between 20°C
and 23°C. The relative humidity of the air should be between 30% and 70%
with air movements less than 0.2 m/s. Noise levels should not exceed
55 decibels.
ITITFact
Fact
The most frequently reported health concern for information technology
participants is vision-related problems. Eye specialists estimate that 36% of
these problems are related to the work environment.
Nature of work
A new information system will change a participant’s work. It will be positive if
the new system involves a variety of tasks and a balance between work and rest.
However, if the new system creates high levels of stress, the impact will be
negative. Stress may result from increased workload, inadequate job design, lack of
social relations or concerns about job security. New systems have an impact on
work in the following areas:
• Use of skills. Participants may be required to retrain and learn new skills
(become multiskilled) or perform work requiring less skills (become deskilled).
• Meaningful work. Participants who work on the computer may not understand
the importance of their work. Their work may be abstract in nature and
focused on symbols on the screen.
• Nature of the workplace. Part-time work and the use of contracted labour may
increase. There is the expectation that workers will continually change jobs
throughout their careers.
• Social relationships. Social interaction may change when a new system is
implemented. For example, people looking at a screen for most of the day tend
to have less social interaction.
Systems and ethics
Ethics is a set of beliefs we hold about what is right and wrong. There are a
number of issues involving the use of information systems that many people are
concerned about. These include environmental damage, equity and access,
invasion of privacy, freedom of information, computer crime and copyright. These
issues will be discussed throughout the text.
Environment
Information systems give us the power to affect the environment. They have the
ability to help us reduce pollution. The use of communication systems has the
potential to reduce the need for transportation and hence air pollution. It allows
people to work from home, regardless of where they live. Communication systems
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also enable people to access electronic services in country areas. This may reduce
the need for high-density housing and the overpopulation of cities.
Conversely, information systems are also increasing the damage to our environment. The manufacture of silicon chips increases the consumption of fossil fuels,
builds mountains of waste and produces toxic chemicals. Paper consumption by
our printers is destroying our forests and increasing our consumption of fossil
fuels. However, our reliance on paper as a medium is decreasing. Compact discs
(CDs) are replacing such books as encyclopedias, and people are reading electronic newspapers and magazines (see Figure 1.6)
Figure 1.6 Electronic newspapers.
Equity
Equity concerns equal rights for all. It means that all people should have equal access
to the benefits of information technology. Information technology has the potential
to give many people equal access to education, employment, medical treatment and
many other benefits. It can overcome differences in race, sex, location or disability.
Communication systems can give people in isolated communities the chance to gain
education that was previously only available in larger cities. New technologies have
allowed people affected by disabilities to better participate in society, gain
employment and have greater freedom. On the other hand, people do not always
have equal access to information technology. People may be disadvantaged because
of the cost of buying and training in the use of the technology.
Gender equity is a concern to many people. They argue that women are not
taking advantage of information technology in the same numbers as men.
Significantly fewer women than men have information technology careers.
Similarly, fewer women than men use the Internet regularly. There are several
reasons for this. There is an image in society that computers are ‘technical’ and
therefore an area more for men than for women. This image is reinforced by
advertising in the media that has traditionally targeted men and excluded women.
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Conversely, it can be argued that the percentages of men and women working in
information technology are roughly the same as in any other industry. The fact
that women are employed in the lowest paid positions, such as data entry
operators, has nothing to do with information technology. Gender equity is an
issue throughout our society. For instance, the number of male doctors is much
greater than the number of female doctors. Furthermore, there are many examples
of women playing a leadership role in information technology.
Exercise 1.2
1 Outline the strengths and weaknesses of people and machines.
2 What are the differences between a machine-centred and a human-centred
system?
3 What is the advantage of a user-friendly information system?
4 What health problems are caused by the incorrect use of computers?
5 Describe the ergonomic recommendations for furniture.
6 What are the environmental factors that affect the work environment?
7 How can a new system create a high level of stress?
8 Describe the impact of new systems on work.
9 How can information systems reduce pollution?
10 Why is gender equity a concern to many people?
LEARNING ACTIVITIES
1 ‘The use of information systems is impacting on our environment.’ Discuss this
statement. Outline your view on this issue.
2 Choose a small business that uses an information system. List the advantages and
disadvantages the use of information technology may have on this business.
Outline some of the issues raised by the use of an information system.
3 ‘Information technology has brought nothing but stress, suffering and deskilling
into modern society.’ Outline your view on this statement.
4 Imagine you are the project leader responsible for the development of a new
system for a large organisation. Describe some of the steps you would take to
reduce any social and ethical problems that might arise from its implementation.
5 The introduction of information systems has led to employment redundancy.
Name and discuss two other social and ethical issues that are commonly associated
with information systems.
1.3 Understanding the problem
Understanding the problem is the first stage in the system development cycle. The
exact nature of the problem must be determined and whether it can be solved by
an information system (see Figure 1.7). This may involve redefining the problem
and identifying its important elements. A clear problem statement is essential at
this stage. Understanding the problem often involves a preliminary investigation
and completing a requirement report. These concepts are briefly outlined here as
they were examined in detail in the Preliminary course.
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Input
• Problem
• Participants
• Data
Ι
Understanding
the
problem
Ο
Output
• Clear problem
statement
• Requirements
Figure 1.7 Block diagram of understanding the problem.
Preliminary investigation
A preliminary investigation, or requirement definition, determines whether a
quick fix of the existing system will solve the problem or a new system is
necessary. The fundamental operations of and problems with the existing system
must be understood. Each of the information processes is examined, and any
deficiencies in the existing system are recorded. The preliminary investigation
takes into account the needs and concerns of all the participants. Participants play
an important part in developing a workable system. Their views are gathered using
different data collection methods, such as interviews, surveys, observations and
measurements. Data is collected to understand the problem and to develop an
appropriate solution. Data collection is very important. If the data is incorrect, the
new system may not meet the needs of the participants.
ITITFact
Fact
It is estimated that participants use only 30% of the software developed for
a new system in the specified manner. The main reason for this statistic is
that developers do not understand what their participants need.
The requirement report is a statement about the need for a new system.
It outlines the aims and objectives of the new system and how it will help the
organisation. The requirement report is based on data collected from the participants. It must match the goals of the organisation to ensure that management is
satisfied with the solution. The requirement report also provides an overview of
the new system in terms of the data/information, information processes and
information technology to be used. The requirement report is used to develop
potential solutions to the problem.
Prototypes
A prototype is a working model of an information system. Prototypes are built in
order to understand the requirements of the system. They also can help in defining
the problem to be solved and in determining how an information system might
solve the problem. Prototypes can be used to test possible information system
features. In this case, participants actively use the prototype to identify both good
and bad features of the new system. Prototypes may contain data entry screens and
a small sample database or may use formulas that provide approximate results.
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A prototype assumes that the participants cannot say exactly what the
proposed information system should do. It proceeds by building a succession of
models. The process is repetitive. That is, the participants evaluate the model, they
suggest improvements, and then another version of the prototype is built. These
three steps are repeated until the prototype successfully solves the problem or the
project is abandoned. Clearly, the later versions of a prototype are more detailed
and accurate. When the prototype has clarified the requirements of the system, it
is either discarded or adapted for more permanent use.
There are three main advantages in using a prototype:
• The requirements of the system more accurately reflect the needs of the
participants. Most participants will better understand the new system if they
use a prototype rather than read the design specifications.
• Participants have the opportunity to be involved earlier and more directly in
the development of the new system. This may reduce the number of changes
required by the participants in the testing, evaluating and maintaining stage.
• The new system is easier to create from a prototype. For example, if a database
management system (DBMS) was used to create a prototype, then some or all
of the forms and reports developed for the prototype could be used to build
the new system.
However, using a prototype has some disadvantages. First, the greater involvement of the participants could impact on their work with the old system. Second,
the repetitive process of the prototype can be frustrating if the succeeding versions
do not provide a better solution. Finally, successful prototypes can produce
software that is difficult to maintain, unreliable or inadequate. This may occur if
any design restrictions are not taken into account when creating the prototype.
Exercise 1.3
1
2
3
4
5
6
7
8
What is essential in the understanding the problem stage?
Describe some of the activities completed in the preliminary investigation.
What is provided by the requirement report?
Why are prototypes built?
What do prototypes contain?
Why is the use of a prototype a repetitive process?
Describe three advantages in using a prototype.
How could a greater involvement of participants in the use of a prototype be a
disadvantage?
LEARNING ACTIVITIES
1 Explain why it is important to involve the participant in the system development
cycle.
2 The first two stages of the system development cycle involve much consultation
with participants. However, participants usually do not have design or programming skills. Why does the project leader rely on information gathered from
participants?
3 Your family would like to create a yearly newsletter that contains the major
achievements of each family member. Create a prototype of the newsletter using
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a software application. Discuss the model with your family and make any modifications. Save the prototype with the filename FAMILY.
4 A teacher at one school requires the students to summarise all the concepts
presented in this course, so a glossary is to be developed. The glossary consists of
key terms, an explanation, text reference and relevant topic. Create a prototype
for this project using a DBMS. The prototype is to contain sample screens and
reports. It should also contain sample data. Save the prototype with the filename
GLOSSARY.
1.4 Making decisions
This stage involves making decisions using the data gathered in the preliminary
investigation (see Figure 1.8). The first task is to develop one or more potential
solutions to the problem. A computer system should be seen only as a tool that
may offer the best solution to the problem. It is not the solution to every problem.
Each potential solution is developed using the requirement report and the scope
of the problem. The scope of the problem places constraints on the new system.
A constraint is a factor that affects the system and prevents it from achieving
the desired objectives. There are different types of constraints, such as financial,
technical, environmental or personal. For example, a financial constraint would be
the amount of money an organisation is prepared to spend to solve the problem.
After establishing several potential solutions, the project leader seeks further
guidance from the management of the organisation. Management receives a
brief written or verbal statement outlining the advantages and disadvantages of each
solution. If the potential solutions seem appropriate, a feasibility study is carried out.
Input
• Problem
statement
• Constraints
• Feasibility
• Data
Ι
Making
decisions
Ο
Output
• Recommendation
• Specifications
Figure 1.8 Block diagram of making decisions.
Feasibility study
A feasibility study is a short report that analyses potential solutions in terms of
the known constraints and makes a recommendation. It does not attempt to find
a detailed solution. The feasibility study briefly examines the available options,
estimates costs and identifies any constraints to be considered. It judges whether
a potential solution can actually be implemented. It should identify the nature of
any problems, indicating the size or magnitude of the problem and whether it
appears to be solvable. The study also needs to indicate the scope or boundaries set
on the development of a new system, such as the maximum cost or the amount
of change that is acceptable. Feasibility studies are an extension of the preliminary
investigation and are divided into different sections (see Table 1.1).
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Section
Content
Title page
Project name, report title, authors, date
Contents
A list of report sections and page numbers
Problem definition
Exact nature of the problem
Requirement report
Aims and objectives of the new system
Summary of investigation
Overview of the existing system; benefits, costs and
constraints of the new system
Alternative solutions
Expanded details of each proposed new system
Recommendations
Recommended course of action; justify the decision
Project plan
Schedule if the recommendation is to proceed
Appendix
Supplementary material, such as surveys, Gantt charts
and diagrams
Table 1.1 Typical sections of a feasibility study.
The initial sections of the feasibility study (problem definition, requirement
report and summary of investigation) state the nature of the problem, list the aims
and objectives of the new system and give an overview of the existing system.
They identify problems or requirements that are not satisfied by the existing
system and outline the constraints on the development of a new system. They also
restate the aims and objectives of the new system more precisely than the
requirement report.
The middle section of the feasibility study analyses the data collected in the
preliminary investigation. It often requires more data to be gathered about each
potential solution. After analysing the data, each solution is briefly described with
its expected advantages and disadvantages. These descriptions are written in terms
of how well they meet the aims and objectives of the new system.
The result of the feasibility study is the recommendation. The recommendation is based on a number of criteria, such as economic, technical, schedule and
organisational:
• Economic feasibility compares the costs of developing the new system with the
expected benefits. A financial analyst is often asked to assess economic
feasibility. Economic feasibility is also called cost/benefit feasibility.
• Technical feasibility determines the information technology requirements of
the new system and the technical demands that will be placed on the new
system.
• Schedule feasibility determines whether time is available to implement the
new system.
• Organisational feasibility determines whether the new system will fit into the
organisation and meet the current goals and objectives. It also determines
whether the new system will have enough support from participants to be
successfully implemented and whether participants can operate the system.
A feasibility study has three recommendation options (no change, develop a
new system or investigate other solutions), and it often examines the effect of
adopting each of these recommendations. The managers of the organisation select
the recommendation that seems most feasible. If the managers decide to proceed
with a new system, then a detailed analysis is completed.
The final section of the feasibility study is the project plan, which was discussed earlier in this chapter.
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Analysis report
If the managers decide to proceed
with a new system, then a more
detailed analysis is required. The
existing system is investigated in
greater depth to ensure all current
operations and problems are
understood. The project leader
must also further clarify the needs
of the new system (see Figure 1.9).
This requires more data to be
gathered, using interviews, surveys,
observations and measurements.
When the data is collected, it must
be organised and analysed. It is
necessary to understand the flow of
data through the system and how
Figure 1.9 Project leader discussing the system
the data is processed within the
requirements with a participant.
system. Various tools are used for
this purpose, and they are described in the next section.
When the detailed analysis is completed, an analysis report is written.
It provides more detail than was presented in the feasibility study. The analysis
report provides a basis for further development. The details of the new system are
presented, along with recommendations for design, implementation and maintenance. The analysis report contains design specifications for the next stage. These
specifications give the general hardware configuration of the new system and designs
for both input and output. The analysis report is the basis for a more detailed project
plan. Remember that the project plan must provide an overall schedule, the details
of the subprojects, and a schedule for each subproject, as well as identify the people,
information technology and data/information required by the system.
ITITFact
Fact
One third of all software projects fail. The major causes of failure are lack of
participant input, lack of managerial support and incomplete design
specifications.
Exercise 1.4
1
2
3
4
5
6
7
8
Describe the second stage of the system development cycle.
What is a feasibility study?
Describe the initial sections of the feasibility study.
What is economic feasibility?
What is determined by organisational feasibility?
What are the options available to management after receiving a feasibility study?
Describe an analysis report?
What are some of the design specifications contained in the analysis report?
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LEARNING ACTIVITIES
1 A new system requires a piece of application software to run on a network. However, the software licence states that the software can only be used on a standalone personal computer. The project leader needs to make a recommendation in
the feasibility study. What options need to be investigated by the project leader?
2 Melissa would like a digital camera so she can include photographs on her Web
site. Analyse the current trends in digital cameras and prepare a list of possible
solutions. Make a recommendation and justify your choice.
3 Terry requires a personal computer for less than $3000 to access the Internet.
Analyse the current trends in the computer market and prepare a set of design
specifications for Terry. The specifications should give the general hardware
configuration of the new system and any software requirements.
4 A feasibility study is to be completed for an online tutorial system for your school:
a List three groups of people who will be affected by the new system.
b For each group, describe some of the possible effects on them.
c Describe some of the factors that will affect the recommendation.
5 Write a feasibility study using the information in the answers to the above
question. It should contain the following sections: title page, contents, problem
definition, requirement report, summary of investigation and a recommendation.
1.5 Designing solutions
Designing a solution is the transformation of the specifications into appropriate
hardware, software and information processes. It involves purchasing hardware,
writing or purchasing software, and specifying information processes to make the
system operational (see Figure 1.10). Systems analysts and programmers often use
a top-down approach to designing a solution. It divides a large, complicated
problem into a series of smaller, easier to solve problems. The smaller problems are
solved and brought together to solve the larger problem. In addition to information
systems personnel developing a solution, it may be developed by a participant.
Input
• Specifications
Ι
Designing
solutions
Ο
Output
• Hardware
• Software
• Information
processes
Figure 1.10 Block diagram of designing solutions.
Participant development
Participant development occurs when people within the information system
develop the solution. Participants produce their own information system using
readily available information technology (see Figure 1.11). Information system
personnel do not develop the system. Software tools for participant development
include general applications, such as spreadsheets and DBMS, and specific
industry applications, such as software developed for real estate and libraries.
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Participant development is used when the project is not a basis for other projects
and reliability is not crucial. For example, a solution created and tested by a team
of programmers will probably be more reliable than one developed by a user who
is creating his or her first solution using a simple spreadsheet.
Figure 1.11 Software tools available on the Internet.
Participant development became a solution because information system personnel were often very busy and unable to provide immediate service. Participants
could solve small problems using application packages and allow the information
system personnel to focus on the major problems. The stages in the system
development cycle are affected by participant development:
• Understanding the problem—participant identifies the problem. Information
system personnel might be used to advise the participant on possible tools to
solve the problem.
• Making decisions—participant chooses an appropriate solution.
• Designing solutions—participant develops the solution, often using guided
processes found in application packages. The participant may require some
training to design a solution.
• Implementation—participant begins using the system. This stage is often easier
to accomplish with participant development than with a system developed by
information system personnel as the participant is familiar with the application
and does not require further training. There is no issue regarding acceptance of
the solution by the participant.
• Testing, evaluating and maintaining—participant is totally responsible for the
maintenance and testing of the solution and determining if any changes need
to be made to the solution.
Participant development is more responsive to participant needs and has the
potential to save time and money. It reduces the involvement of information system
personnel. There is no need for programmers. In addition, the participant does not
have to communicate his or her needs during the initial stages, and training in the
implementation stage should be reduced. However, there are some disadvantages:
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• Participants who develop a solution are not hardware experts. Information
system personnel often make more informed decisions and may receive a
discount for bulk purchases. They also have specialised knowledge about the
particular equipment that they purchase.
• Applications and the operating system chosen by a participant may be different
to those used by other participants in the organisation. This creates additional
costs in terms of site licences and training. Incompatible software makes it
difficult for people to work together.
• Participants need access to data for their solutions. This creates security
problems. Downloading data to a disk and transferring it to another computer
increases the risk of the data being stolen.
Participant development could also be a component of the system development cycle. First, the core of the information system is created by the information
system personnel based on the design specifications. Second, the participants
develop the user reports and screens using a fourth-generation language (4GL)
that can be taught to users. This approach maintains control of the system while
providing some of the advantages of participant development.
Design tools
Design tools assist in the development of a new system. They describe the
information processes and rules within the system. Design tools include context
diagrams, data flow diagrams, system flowcharts, decision trees, decision tables and
data dictionaries.
Context diagrams
A context diagram is a graphical method of representing a system that uses only
a single process together with inputs and outputs (external entities). There are
only three symbols in a context diagram: the process, data flow and external entity
(see Table 1.2). The external entities are linked to the single process by data flow
arrows. A context diagram is often the starting point of a data flow diagram
(discussed below). The context diagram in Figure 1.12 shows a system for
searching the Internet. It clearly shows the flow of data in the system.
Symbol
Meaning
Single process: A circle is used to represent the entire
system.
Process
Data flow: An arrow is used to represent the flow of
data between the process and external entities.
External
entity
External entity: A square or rectangle represents any
person or organisation that sends data to or receives
data from the system.
Table 1.2 Symbols used in a context diagram.
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Core
Student
Keywords
Use
search
engine
Internet address
Student
Figure 1.12 Context diagram for searching the Internet.
Data flow diagrams
A data flow diagram (DFD) is a graphical method of representing a system that
uses a number of processes together with inputs, outputs and storage. A DFD
focuses on the flow of data between information processes in a system. It shows
where data is collected, organised, analysed, stored, processed, transmitted and
displayed. DFDs provide a simple technique for visualising the movement of data
and describing what participants do rather than what the computers do. There are
four main symbols in a DFD: the process, data flow, data store and external entity
(see Table 1.3).
Symbol
Meaning
Process: A circle is used to represent the processes or
actions that transform inputs to outputs.
Process
Data flow: An arrow is used to represent the flow of
data between the process, external entity and data store.
Data
store
External
entity
Data store: An open rectangle represents the location
where data is stored. It could be a filing cabinet, hard
disk or DVD.
External entity: A square or rectangle represents any
person or organisation that sends data to or receives
data from the system.
Table 1.3 Symbols used in a data flow diagram.
The data flows and data stores are given names to describe the data. The
processes should contain a description of the change in data. Each process must
contain at least one input and at least one output. The DFD in Figure 1.13
illustrates the movement of data for searching the Internet. To draw a DFD, start
with the processes and link them to data stores and external entities using data
flows. It is often easier to start with a simple diagram, such as a context diagram,
and then add some more details. If the DFD becomes too complicated, it should
be broken down into a smaller DFDs. This creates different levels. The top-level
DFD identifies the major processes while lower-level DFDs add the detail.
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DFDs and context diagrams are easy to understand as there are only three or
four symbols. Participants can see what tasks are completed by the information
system. Context diagrams and DFDs often identify issues of responsibility before
the system is designed. However, the simplicity of these design tools creates
certain limitations. For example, they do not show the sequence of operations or
decisions that are needed by a programmer.
Student
Keyword
Use
search
engine
Internet address
Load
Web site
Internet
address
Keyword
Database
of
Web sites
Graphic
Project
Figure 1.13 DFD for searching the Internet.
Decision trees and decision tables
The information processes that operate on data in most information systems are
determined by decisions. These decisions are made on the basis of the data entered
into the system according to a set of rules or conditions. Two tools used to display
and analyse decisions are decision trees and decision tables.
A decision tree is a diagrammatic way of representing all possible combinations
of decisions and their resulting actions. It represents the decisions made within a
system as the branches of a tree. Each branch ends with a particular action. The
decision tree in Figure 1.14 shows decisions made when searching the Internet.
It is applying rules based on the number of hits.
Condition
Search
Number of Web
sites is greater
than 10
Use a more
specific search
Number of Web
sites is less
than 10
Access each Web
site
No result
Try a new keyword
Figure 1.14 A decision tree for searching the Internet.
22
Core
Action
A decision table is a table that represents all possible conditions and actions.
It indicates the alternatives for different conditions and actions based on the rules.
The table is divided vertically into conditions and actions, and then horizontally
into rules. The decision table in Figure 1.15 shows the decisions made when
searching the Internet. Decision tables are often more difficult to understand than
decision trees, especially when decisions are based on previous decisions.
Conditions
Rules
Number of Web sites is greater than 10
✓
✘
✘
Number of Web sites is less than 10
✘
✓
✘
No results
✘
✘
✓
Use a more specific search
✓
✘
✘
Access each Web site
✘
✓
✘
Try a new keyword
✘
✘
✓
Actions
Figure 1.15 A decision table for searching the Internet.
Data dictionary
A data dictionary describes the data within the system. It is a tool used to manage
the information resources. A data dictionary is often used to assist the design and
check the accuracy of data flow diagrams. It is also a starting point for designing
screens and reports. (See Figure 1.16.)
Data item
Web site
Internet address
Author
Start
Keyword
Description
Domain name of Web site
Unique address
Name of author
Date created (dd/mm/yy)
List of keywords
Example
www.hi.com.au
205.188.200.58
Bloggs, Joe
02/12/99
technology, computer
Figure 1.16 A data dictionary of Web sites.
A data dictionary also describes each field in the database. It provides
information about the characteristics of each item entered in the database, such as
the field names, field sizes, data types and field descriptions. Data dictionaries may
contain validation rules that specify appropriate codes, ranges or values for each
data item. For example, a validation rule for a data item named State might only
allow participants to enter one particular abbreviation for each state name, such
as NSW for New South Wales or QLD for Queensland.
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System flowcharts
A system flowchart is a graphical method of representing both the flow of data
and the logic of a system. It documents the essential details of the system, such as
the sequence, the processes, and the precise rules for selecting particular actions.
A system flowchart also shows the hardware used to process data, such as the
peripheral devices, storage mediums and processing units.
System flowcharts use standard flowcharting symbols plus special symbols for
peripheral devices (see Table 1.4). Some of these symbols have become out of
date, such as the punch card symbol. Each symbol contains messages and is linked
by lines called flowlines.
Symbol
Meaning
Symbol
Meaning
Input/output
Manual operation
Paper document
Magnetic tape
Online display
Direct access
storage device
Online input
Flowline
Punched card
Telecommunications
link
Process
Predefined process
Terminal
Decision
Table 1.4 Symbols used in a system flowchart.
The system flowchart in Figure 1.17 clearly illustrates the logic of a system
for finding information on the Internet. It shows the sequence, selection and
repetition involved in the system.
24
Core
Begin
Internet browser
Access search engine
Enter keywords
Search results
Access a Web site
Read data
False
Is data
appropriate?
True
Project
False
Are you
finished?
True
End
Figure 1.17 System flowchart for finding information on the Internet.
Exercise 1.5
1 Describe the third stage in the system development cycle.
2 What is participant development?
3 How are the stages in the system development cycle affected by participant
development?
4 Describe three disadvantages of participant development.
5 Name and describe the three symbols of a context diagram.
6 What is a data flow diagram?
7 Name and describe the four symbols of a data flow diagram.
8 What is the difference between a decision tree and a decision table?
9 Describe some of the information provided by a data dictionary for a database.
10 What is a system flowchart?
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LEARNING ACTIVITIES
1 Why is it important to consider how data is manipulated by a system in the system
development cycle?
2 A study system is a process to improve HSC results. Students decide the subjects to
be studied and the amount of time required. The study system produces the
knowledge and understanding needed for the HSC examination. Construct a
context diagram for the study system.
3 The study system in question 2 is extended to include a table and a tutor. The table
lists the subjects and time allocations. Construct a data flow diagram to show the
study system.
4 The table in question 3 is created using a word processor by following these
processes: enter subjects and time, save data, format table, edit table if required,
print table. Construct a system flowchart for the study system.
5 An organisation intends to pay a bonus to some of its employees. To be eligible for
the bonus, an employee must have worked for the organisation for at least two
years. Managers get $700 and other employees get $500. Construct a decision tree
and a decision table to clarify this process.
6 Al’s Mechanical Repairs has developed a policy for accepting a customer’s cheque.
The cheques will be accepted if all of the following conditions apply: cheques are
less than $300, current driver’s licence is shown, and customer’s signature matches
driver’s licence signature. Construct a decision tree and a decision table to clarify
this process.
7 A shoe store offers a discount on the number of shoes purchased by the customer.
If customers buy one pair of shoes, they receive no discount; two or three pairs of
shoes, they receive a discount of 10%; and more than three pairs of shoes, a
discount of 15%. In addition, if their purchases are greater than three pairs of
shoes and exceed $200, they receive a further discount of 5% (for a total discount
of 20%). Construct a decision tree and a decision table to clarify this process.
1.6 Implementing
The implementation stage delivers the new system to the participants. It involves
using the solution to solve the problem (see Figure 1.18). The implementation
stage may involve a major change in the way the organisation operates. To ensure
the new system is successfully implemented, it must be carefully planned.
Implementation procedures need to be carried out in the correct order. For
example, it is necessary to ensure the hardware of a system is installed before the
software is set up. Large projects require an implementation plan to detail the
participant training, the conversion method and the system testing.
Input
• Solution
• Training
• Conversion
• Testing
Ι
Implementing
Figure 1.18 Block diagram of implementing.
26
Core
Ο
Output
• Using new
system
Participant training
Training ensures participants can use the new system and understand its benefits.
Training is also needed in the installation of a new system and to ensure that the
computer is being used efficiently. The type of training depends on the existing
knowledge of the participants and the features of the new system.
Training is provided by range of different people and technology (see Figure
1.19). Management may decide to train one person who has responsibility for
training other people. The suppliers of the hardware and software may carry out
some training. Training specialists instruct participants in how to operate their
system. Training manuals and presentations are used to explain the
new system and any changes in the
information processes.
Initial training is completed
before the old system is converted
to the new system. Participants
may also need training updates to
keep pace with the latest developments in hardware and software.
Technical support staff are
people who assist participants of a
system on an as-needed basis. Their
services are usually provided over
the phone. Technical support staff
need to be completely familiar
with the system.
Figure 1.19 Multimedia used for training.
Conversion method
The method of conversion is the way in which the information processes
performed by the old system will be transferred to a new system. It must be
carefully planned and executed to avoid errors. The method chosen for conversion
depends on the nature of the work and the characteristics of the new system.
There are four methods of conversion: direct, parallel, phased and pilot.
Direct conversion involves the immediate change to the new system on a
chosen date. On that date, the old system ends and the new system starts. All data
from the old system is transferred to the new system, and the participants stop
using the old system and begin using the new system. Direct conversion is not
commonly used even though there are minimal transition costs. One reason that
direct conversion is not commonly used is that it does not allow the project team
to check whether the new system will operate correctly and whether participants
understand the system. Another reason is that, if the new system fails or problems
occur, the old system is not available as a backup.
Parallel conversion involves the old and new systems both working together at
the same time. Participants can compare both systems and obtain a good
understanding of the differences between the systems. If there are any problems
with the new system, it can be solved before the old system is discontinued.
However, parallel conversion results in additional workloads for participants as
they must operate both systems until the new system is accepted. It may also
result in confusion about which system has the correct data.
Phased conversion involves the gradual implementation of the new system.
Certain operations of the new system are implemented while the remaining
operations are completed by the old system. When one operation of the new
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system is successful, another operation is implemented until the new system is
fully operational. Each operation is individually tested. If there is a problem with
a certain operation, it is possible to switch back to the old system. Unfortunately,
phased conversion is often confusing because some participants are on the old
system and some are on the new system.
Name
Method of conversion over time
Direct conversion
Old system
New system
Parallel conversion
Old system
New system
Phased conversion
Old system
New system
Pilot conversion
Old system
Old system
Old system
New system
New system
Figure 1.20 Methods of conversion.
Pilot conversion involves trialing the new system in a small portion of the
organisation. The old system is still available if the new system fails or experiences
problems. Pilot conversion is usually started by a keen group of participants who
appreciate the benefits of the new system. If pilot conversion works, it is usually easier
to motivate the other participants of the organisation to change to the new system.
System testing
Testing a system is a very important part of the
implementation of a system. Without rigorous
testing, the system cannot be guaranteed to work as
expected. Tests must be designed to examine the
system operation under all possible events. It is
necessary to test both the information technology
and the information processes:
• Hardware is tested using diagnostic software and
through general operation (for example, the
speed and resolution of a printer). Backup
systems should be tested by selecting files to be Figure 1.21 Magnetic tape
restored (see Figure 1.21).
used for backup.
• Software is tested using data that has been
structured to test all decisions made within the system. This test data must
cover all possible combinations of data that may be encountered. It should be
based on the original design specifications.
• Information processes are continually tested during the implementation of the
system over a period of time. Minor changes to procedures are immediately
implemented.
28
Core
Exercise 1.6
1
2
3
4
5
6
7
8
9
Describe the fourth stage of the system development cycle.
List the contents of an implementation plan for a large project.
Why is participant training necessary?
Describe some of the training provided by training specialists.
List the four methods of conversion.
What are the risks of implementing a new system using direct conversion?
Explain the difference between parallel conversion and phased conversion.
Why is testing a system very important?
What is test data?
LEARNING ACTIVITIES
1 Write an outline of a training program to help beginners use the Internet.
The training program should include accessing Web sites, using domain names and
using search engines. The training program must specify a list of appropriate
Web sites.
2 What is the method of conversion in which a new computer system is developed
and implemented alongside the old system until the new system is working well?
Outline the advantages and disadvantages of this system.
3 A project leader is preparing to meet management and participants to discuss the
method of conversion to a new system. At this meeting, the project leader wishes
to discuss two alternative conversion strategies. Compare and contrast two
methods of conversion that could be proposed by the project leader.
4 A school is implementing an electronic attendance system. This will replace the
manual method of checking students’ attendance. Initially, the new system will be
used to check the attendance of one group of students. The number of groups will
be gradually increased until the system is fully implemented. What is the method
of conversion to the new system? Do you think it is the best method of conversion
for this project? Why?
1.7 Testing, evaluating and maintaining
After the new system is fully implemented, participants expect the system to be
working correctly. The successful operation of a system involves the information
technology working correctly and the participants using it effectively. People
responsible for operation of the system include computer operators and managers.
Input
• Using new
system
Ι
Testing,
evaluating and
maintaining
Ο
Output
• Modifications
• Upgrade
Figure 1.22 Block diagram of testing, evaluating and maintaining.
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29
Computer operators perform tasks on
the equipment, such as monitoring
performance, starting up, running jobs and
backing up. The operators manual is used
to specify tasks to be completed on a
regular basis. If there are problems and the
system breaks down, the problems must be
diagnosed and corrected immediately. The
computer operator attempts to identify
the problem and, if necessary, liaises with a
technician to rectify the problem.
Managers are responsible for the
effective use of the system. They oversee
the computer operation and ensure that
Figure 1.23 Managers of a system.
participants and machines work efficiently
(see Figure 1.23). There are many different types of managers with slightly different roles. An information systems manager plans and oversees all the information
resources in the organisation.
After the new system has been in operation for a number of months, it must be
tested and evaluated.
Testing and evaluating
In this stage, the performance of the system is tested and then evaluated. Testing
a solution ensures that it works. Testing is carried out throughout the system
development cycle. Evaluation determines whether the system is working as
expected or whether changes are required. It occurs after the new system is
established and minor problems have been fixed. The project leader, in consultation with participants, often completes an evaluation. It is based on interviews,
surveys, observations and measurements. During an evaluation, the results of the
new system are compared to the initial aims and objectives outlined in the
requirement report.
Evaluation is ongoing. If the new system is not performing, then changes need
to be made. If a major upgrade is required, then the system development cycle
starts again. The results of the evaluation are the basis for understanding the
problem in the next cycle. Information systems are involved in a constant process
of evaluation, analysis and development to improve their efficiency. Evaluation is
also used to improve the processes involved in the system development cycle. In
some situations, evaluation results in the system undergoing maintenance.
ITITFact
Fact
Microsoft builds software products by first identifying the new capabilities
that customers request and then identifying any features it wants to include
for its own strategic reasons.
Maintenance
Maintenance is the modification of the system by making minor improvements.
During the operation of the system, participants may discover deficiencies in the
system and suggest improvements. For example, a secretary may suggest some
change in the format of an input screen. Maintenance may also involve installing
30
Core
new hardware and upgrading software
packages. The longer the system has
been operational, the more difficult it is
to change. However, good documentation makes it easier to undertake
maintenance without causing problems
elsewhere. Simple changes in a large
information system are often complex to
implement and require retesting of other
parts of the system. This often results in
starting the system development cycle
again. The tasks in this stage are ongoing
and continue until another system is
developed or the system is terminated.
Operation manual
An operation manual details procedures participants follow when using a new
system. Participants need to be instructed about and assisted with the major
features and functions of the system. To create an operation manual, it is necessary
to determine the background of the participants. This will determine the format,
language and depth of instructions required. A beginner will need simple
instructions using non-technical language and may need additional guidance, such
as tutorials. The operation manual is usually presented as a hard copy, although
online versions are frequently available. Some of the factors for creating an easyto-use operation manual include:
• user-friendly format and structure
• clear and concise instructions
• steps listed in point form
• tasks completed in the simplest way
• appropriate instructions for file management and security
• screen dumps included where possible.
Case study
Port Nelson Tourism
Port Nelson Tourism is a small, privately
owned business that works with the local
community to promote the region’s tourist
attractions. It produces printed material
to advertise tourist attractions, such as
beaches, fun parks, sporting activities and
cruises. The promotional material is distributed at tourist information booths,
motels, tourist attractions and shopping
centres. Port Nelson Tourism receives
income by charging businesses for inclusion
in their printed material and by selling
advertising space.
Port Nelson Tourism would like to
expand their business by developing a
restaurant guide. This guide would be
aimed at both tourists and local residents.
To develop a solution, the manager of Port
Nelson Tourism completed the system
development cycle:
• Understanding the problem—a meeting was arranged with the owners of
the major restaurants in the region. This
provided general directions about the
possible formats and typical information to be included. Then a survey was
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31
sent out to all restaurants, and this data
was analysed to determine the requirement report.
• Making decisions—a feasibility study
was completed that recommended a
40-page booklet be published for the
summer season and that two additional
staff be contracted for the project. A
project plan was then developed to
schedule subprojects, such as data
collection and graphics. The analysis
report outlined specifications for the
required information technology and a
more detailed costing. A process of
checking was to be implemented to
validate the data.
• Designing solutions—a data flow
diagram was used to specify the information processes and the flow of
data. Each restaurant was visited, the
employees were interviewed, and
photographs were taken. A highperformance personal computer and a
digital camera were purchased along
with a word processing program,
painting program and desktop publishing program. A template for the
publication was created to ensure
consistency. Ergonomic furniture was
purchased in consultation with the staff.
• Implementing—staff were given some
brief training with the new system, as
they were experienced users. The booklet was created in a desktop publishing
program by importing the text from a
word processing program and the
graphics from a painting program. Each
restaurant was given a draft copy of the
booklet before publication.
• Testing, evaluating and maintaining—
the new system was monitored
throughout the implementation stage,
and changes to the front page design
were suggested. At the end of the
summer season, a series of interviews
were completed to evaluate the performance of the finished product. The
feedback was positive; however, some
changes to the structure of the booklet
were suggested. The manager of Port
Nelson Tourism evaluated the project
and recommended a second edition be
published next year.
Exercise 1.7
1
2
3
4
5
6
7
8
Describe the final stage of the system development cycle.
What does the computer operator do if the system breaks down?
Describe the role of a manager.
What is testing?
How is a new system evaluated?
List two tasks that may be performed during maintenance.
What is an operation manual?
Describe some of the factors for creating an easy-to-use operation manual.
LEARNING ACTIVITIES
1 Why should a new system be evaluated after installation?
2 If a system is designed correctly, it should carry out the required tasks. Why is there
a need for ongoing testing and evaluation?
3 A desktop publishing program was part of the solution in the case study.
Investigate the latest desktop publishing software. Suggest the most appropriate
packages for this situation. Justify your answer.
4 A high-performance personal computer was mentioned in the case study. Describe
a high-performance personal computer. List any peripheral devices that would be
required by Port Nelson Tourism to implement its new system. Investigate the
options and costs of each device. List these details.
5 Interviews were part of the evaluation in the case study. Which people should be
interviewed? Make a list of interview questions that could be used to evaluate the
restaurant guide.
32
Core
Chapter review
PART A
Select the alternative (A, B, C or D) that
best answers the question.
1 A diagram where the vertical axis lists
the tasks and the horizontal axis shows
the time frame is called a:
A decision table
B Gantt chart
C system flowchart
D data flow diagram
2 A system designed to make participants’ work as effective and as satisfying as possible is called:
A equity system
B human-centred system
C participant system
D ethical system
3 The third stage in the development of a
new system is:
A understanding the problem
B implementing
C making decisions
D designing solutions
4 During the development of a project,
the details of the time schedule occur in
the:
A feasibility study
B prototype
C project plan
D operation manual
5 In the feasibility study, the project
leader focuses on:
A the appropriateness of a solution
B the cost of the new system
C designing a system to meet the
participants’ needs
D how the existing system works
6
7
8
9
10
In a data flow diagram, a person who
receives data would be represented by a:
A external entity
B data flow
C process
D online output
The conversion method where the old
and new systems both work together at
the same time is called:
A pilot
B direct
C parallel
D phased
When a new system is not meeting the
original requirements of the problem, it
is necessary to:
A change the management
B retrain the participants
C restart the system development cycle
D evaluate the system
In which stage of the system development cycle is a decision tree used?
A testing, evaluating and maintaining
B understanding the problem
C implementing
D designing solutions
The most likely location for the description of data is a:
A operation manual
B data manual
C data dictionary
D data validation
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33
Chapter review
PART B
For each of the following statements, select
from the list of terms the one that most
closely fits the statement. Write the letter
corresponding to your choice next to the
statement number.
Statements
1 A table that represents all possible
conditions and actions.
2 The immediate change to the new
system.
3 The process of planning, scheduling
and controlling all the activities within
each stage of the system development
cycle.
4 A series of stages used in the development of a new information system.
5 The general hardware configuration of
the new system and designs for both
input and output.
6 A short report that analyses potential
solutions and makes a recommendation.
7 Determines if a quick fix of the existing
system will solve the problem or a new
system is necessary.
8 A working model of an information
system built in order to understand the
requirements of the system.
9 When people within the information
system develop the solution.
10 A graphical method of representing a
system using a number of processes
together with inputs, outputs and
storage.
11 The gradual implementation of the
new system.
12 Details the procedures participants
follow when using a new system.
List of terms
a data flow diagram
b decision table
34
Core
c
d
e
f
g
h
i
j
k
l
direct conversion
feasibility study
operation manual
participant development
phased conversion
preliminary investigation
project management
prototype
specification
system development cycle
PART C
Write at least one paragraph on each of the
following.
1 What is a Gantt chart? Draw a Gantt
chart for the activities you completed
today.
2 Briefly outline some of the ergonomic
issues that impact on the design of a
new system.
3 Why do people create a prototype?
How are prototypes used to develop a
new system?
4 Describe the typical sections of a
feasibility study.
5 Explain the use of the following tools in
the design of a new system:
a decision table
b data dictionary.
6 What are the reasons for participant
development? Describe some of the
tools used for participant development.
7 Pilot conversion is used in the implementation stage of the system development cycle.
a Explain the process of pilot conversion.
b What are the advantages and disadvantages of using pilot conversion?
8 Describe the final stage of the system
development cycle.
2
chapter
I N F O R M AT I O N
SYSTEMS AND
D ATA B A S E S
Outcomes
processes (H3.2)
Overview
The emphasis in this chapter is on the information processes of organising, storing and
retrieving with database systems and hypermedia. You will gain a greater understanding of
information systems and develop skills with
relational databases.
2.1 Information systems
In the Preliminary course, you studied the basic concepts of an information
system. Information systems perform a set of information processes requiring
participants, data/information and information technology. They perform the
information processes of collecting, organising, analysing, storing/retrieving,
processing, transmitting/receiving and displaying information. The relationship
between the elements of an information system is described in Figure 2.1. The
links between the elements are represented using arrows. Information systems are
created for a purpose and operate in a particular environment.
INPUT
PROCESSING
CONTROL
ST ORAGE
OUTPUT
OUTPUT
Figure 2.1 Information system.
Characteristics of information systems
Information systems are created to provide access to information for an organisation or individual. For a large number of information systems, the data is held in a
database and access is achieved using a DBMS. The characteristics of an information system are the:
• Organisation of data into information. Data must be organised before it can be
stored and analysed by the information system. Careful thought is needed to
organise data; otherwise, the resulting information will be meaningless.
Organising may require sorting, summarising or classifying. Data in an
information system is organised into data structures using such organisational
methods as data dictionaries.
• Analysis of information to give knowledge. Access to information and the
resulting knowledge is the purpose of an information system. For people to
gain knowledge from information, the information must be analysed.
Information systems provide a range of tools for the analysis of data, such as
tables, queries and reports. People make decisions based on the information
they receive from an information system.
36
Core
ITITFact
Fact
A spider or crawler is a program that visits Web sites and reads their pages
to create entries for a search engine. It is called a spider because its ‘legs’ span
a large area of the ‘Web’.
Types and purposes of information systems
The types of information systems and their purposes are changing with developments in information technology. These types and purposes are also not mutually
exclusive. They often overlap and change as new applications or new versions of
existing applications are introduced.
Five types of information systems are examined in this section.
Transaction processing systems (TPSs) collect, store, modify and retrieve the
daily transactions of an organisation. Some examples of the application of TPSs
are buying goods at a point-of-sale (POS) terminal, processing credit card payments and tracking receipts of materials from suppliers. Organisations rely heavily
on their TPS. A breakdown will disrupt operations or even stop the business. For
this reason, well-design backup and recovery procedures are essential. There are
two types of transaction processing: batch processing and real-time processing.
Batch processing collects the transaction data into a group and processes it later.
It is currently used where transaction data is on paper, such as processing cheques.
Batch processing has a time delay, and this may be a significant disadvantage. In
real-time processing, each transaction is immediately processed. It provides instant
confirmation of a transaction but does require access to an online database.
Decision support systems (DSSs) assist people to make decisions by providing
information, models and analysis tools. A DSS can be used on a daily basis or when
an organisation has to react to something unexpected or make changes. One
example of a DSS is a system that analyses the stockmarket and helps the user
make decisions about buying and selling shares. A DSS creates a mathematical
model of the variables affecting the decision, using statistical tools, databases,
spreadsheets and graphics. The model allows a manager to ask what-if questions
by changing one or more of the variables and seeing the projected results. What
would happen if the price were raised? What would happen if the organisation
changed the design of its package? The DSS depends on the accuracy of the
mathematical model and the ability of the manager to formulate appropriate
questions. Expert systems are a type of DSS.
Expert systems provide information and solve problems that would otherwise
require a person experienced in that field (an expert). They are useful in
diagnosing, monitoring, selecting, designing, predicting and training. An expert
system asks users a set of questions and compares their answers to a knowledge
base. The knowledge base is a set of general facts and if-then rules supplied by an
expert. The expert system must reason to obtain a possible solution. For example,
one expert system has been designed to help doctors diagnose infectious blood
diseases and prescribe antibiotics (see Figure 2.2). The system uses the patient’s
medical history, symptoms and laboratory test results as its input and compares
these to its knowledge base. If a match occurs, the system uses its pharmacological
knowledge base to recommend an antibiotic. The solutions from an expert system
are not always correct, and it is up to the user to accept or reject the solution.
37
Figure 2.2 Expert systems are used in medicine.
Management information systems (MISs) provide information for the
organisation’s managers. An MIS presents basic facts about the performance of the
organisation. Some common examples of MIS output are reports on sales, stock
inventory, payroll, orders and budgets. The fact that people are aware of how the
performance is measured helps managers motivate workers and make decisions.
A special type of management information system is called the Executive
Information System (EIS). The EIS is designed for the information needs of senior
managers and provides information on strategic issues, using data from the share
market, commodity prices, interest rates and other economic indicators.
Office automation systems provide people with effective ways to complete
administrative tasks in an organisation. An office automation system uses a range
of software tools, such as word processors, spreadsheets, databases, desktop
publishing, presentation programs and project management software. Office
automation systems also use communications technology, such as Web browsers,
email, facsimile, and video-conferencing. In office automation systems, letters and
documents are constructed quickly, edited if required and easily stored for future
reference or re-use. Email improves productivity by delivering messages and data
more quickly than the paper-based interoffice mail system could. Desktop
publishing software is used to create high-quality flyers, reports and brochures.
Examples of database information systems
Most information systems store data in a database. Information systems that use a
database are called database information systems. You will remember from the
Preliminary course that a database is an organised collection of data. Databases are
accessed by a database management system (DBMS). A DBMS has no data in it.
It is a software package that allows the user to enter, maintain and provide access
38
Core
to a database. The user can choose which data is required and how to display that
information in a meaningful way. The term database is often used instead of
DBMS.
There are many examples of database information systems, such as school
databases that hold information on teachers, subjects, classrooms and students.
This chapter will use the Address and School databases to explain the important
concepts involved in a database information system. Two other examples of
database information systems are the RTA holding information on automobiles
and video stores holding information on borrowers and videos. These latter two
examples are used in case studies in this chapter.
Case study
MovieTime Video
MovieTime Video is a store that uses a
database information system. The store’s
purpose is to hire videos and sell associated
products. The environment is not only the
contents of the store but such factors as
location, communications, suppliers, competitors and borrowers. MovieTime uses a
POS system, and electronic funds transfer
at point of sale (EFTPOS) is available.
MovieTime Video performs a set of information processes that requires participants, data/information and information
technology (see Figure 2.3).
Purpose
• Hire videos and sell associated products
• Scan video/card
• Save database
• Transfer data
• Search database
• Update data
• Display information
Participants
Data/
Information
Information
Technology
• Manager
• Member data
• Personal computer
• Staff
• Video data
• Barcode reader
• Barcodes
• Database
• Receipt
Information System
Figure 2.3 Hiring a video at MovieTime.
39
A database is used to store membership
data, video data and all video transactions.
When new customers come into the store,
they fill out a membership form containing
personal details. The membership data
consists of their last name, first name,
address, home phone number, date of
birth, and work phone number. The data is
entered into a membership table. New
customers select a personal identification
number (PIN) and receive a membership
card with a barcode. When the store buys
a new video, data is entered into the video
table. The video data consists of an identity
number, title, main stars, rating, and an
entertainment category. The videos are
also barcoded for efficient processing.
When a customer borrows a video, the
membership and video barcodes are both
scanned. This data is automatically inserted
into the membership and video tables (see
Figure 2.4).
The participants at MovieTime Video
are continually carrying out the information processes. These processes are not
completed in any order. The staff can move
from collecting the data to displaying the
information. The information processes
include:
• collecting—scanning the video bar-code
• organising—searching the database for
membership details
• analysing—determining the type of
information required (see Figure 2.5)
• storing and retrieving—saving the database to a disk
• processing—updating the data after it
has been entered
• transmitting and receiving—transferring the data between peripheral
devices
• displaying—obtaining a report on a
member’s transactions (see Figure 2.6).
Card, PIN, cash
Member
MovieTime
Video
Video, receipt
Transaction
data
Member data
Video data
Video
database
Figure 2.4 Flow of data at MovieTime Video.
40
Core
Figure 2.5 Constructing a query for MovieTime Video.
Figure 2.6 The results of the query in Figure 2.5.
Exercise 2.1
1
2
3
4
5
6
7
8
9
What is an information system?
List five types of information systems.
Explain the difference between batch processing and real-time processing.
What factors is a DSS dependent on?
Where are expert systems useful?
What is the knowledge base in an expert system?
What information is presented by an MIS?
Describe an office automation system.
The following questions relate to the MovieTime Video case study:
a What is the purpose of MovieTime Video?
b Describe the participants, data/information and information technology.
c List the data in the membership table.
d List the data in the video table.
e Describe the information processes at MovieTime Video.
LEARNING ACTIVITIES
1 Information systems are making unprecedented changes to our society. Briefly
describe the effect of information systems on your way of life. Then select one
impact of an information system that you regard as the most significant. Give a
reason for your choice.
41
2 ‘New office automation systems do not always result in increased productivity.
Workers often spend too much time on relatively unimportant tasks, such as
reformatting documents, organising irrelevant data or surfing the Web.’ Do you
agree with these statements? Why? What steps should be taken by the manager
to ensure office automation systems are used productively?
3 Developing an effective expert system requires a large database and powerful
software. Constructing the knowledge base is expensive and requires human
experts who are willing to provide the data in a suitable form. Consider these
issues and then outline some areas where expert systems could be used effectively.
Are there any areas where expert systems should not be used?
4 Construct a data flow diagram to describe the flow of data in an existing
information system. Choose an information system that you use regularly.
5 In the MovieTime Video case study, the staff could store the history of the videos
borrowed by a particular person as well as the address of that person. This data
could be valuable information to many other businesses, such as book companies.
Outline the ethical issue raise by this situation. What is your view on this issue?
2.2 Organisation methods
Organising is the process of arranging, representing and formatting data.
It involves the concept of a database. A database is an organised collection of
data. People have used this concept of a database throughout the existence of the
human race.
Non-computer and computer-based methods
People need to keep information about themselves and their activities. Common
databases in the home include telephone books, dictionaries, recipe files, encyclopedias or even a list of things to be done. A database is simply a place to organise
and store data so that it can be
retrieved later for a particular purpose. A telephone book is a noncomputer database that organises
data alphabetically according to a
person’s family name. Searching
for the person’s name retrieves
their phone number. A paper
filing system is a non-computer
database. It involves paper, folders
and filing cabinets to store data in
an organised way (see Figure 2.7).
Searching the folders in the filing
cabinet retrieves a single piece of
paper.
Non-computer databases are
often the best way to organise data.
It is convenient to obtain information from a book or access it
from a filing cabinet. People can
Figure 2.7 Non-computer databases have been
easily and inexpensively organise
used for years.
data using a non-computer data42
Core
base. They do not need a computer or computer skills. Non-computer databases
are easier to keep secure, and they remain more private. The data is more difficult
to use for other purposes. For example, a telephone book does not allow a thief to
search for an address and find the phone number of a house.
Computer-based databases are being increasingly used to organise and store
data. Some examples include taxation records, library systems, car registrations,
student records, CD-ROM encyclopedias and census data. Computer-based
databases have several advantages over non-computer databases:
• Easily edited. Data can be corrected and updated without having to retype all
the data.
• Large storage. Data is stored on a disk and retrieved when required.
• Fast retrieval. Data is searched and sorted quickly and accurately to obtain the
required information.
• Display options. Data is presented in a variety of ways, using tables, forms and
reports to suit most purposes.
Computer-based methods of organising include flat file systems, database
management systems and hypermedia.
Flat file databases
A flat file database organises data into a single table and is suitable for many small
applications. Flat file databases organise data using data structures called files,
records, fields, and characters (see Figure 2.8):
• A file is a block of data. When you have done some work on the computer, it
is stored in a file. The Address database is a file. A file in a database is divided
into a set of related records.
• A record is a collection of facts about one specific entry in a database. In the
Address database, a record is information about a person’s name, address and
home phone. A record is divided into one or more related fields.
• A field is a specific category of data in a database. In the Address database, the
family name, given name, street, suburb, postcode and home phone are fields.
Data items in a field are made up of characters.
• A character is the smallest unit of data that people can use. Characters include
letters, numbers, and special symbols.
Field
Record
Character
Figure 2.8 Part of the Address database.
Keys are fields that are used to sort and retrieve information. Usually, each key
holds a unique item that applies to only one record. When the records are sorted, the
key is used so that not all the data has to be read or retrieved. There are different
types of keys, such as a single key, composite key, primary key and secondary key:
43
• A single key is a field in which each item of data is unique. Care must be taken
when choosing a single key, as some fields, such as Family Name, are not always
unique.
• A composite key, or compound key, is made by joining two or more fields
together. It is used when no data item in any field can be guaranteed to be
unique. For example, a compound key can be made from such fields as Gender
and Date of Birth.
• A primary key is a single key or compound key that must have a value. Primary
keys cannot be empty or null.
• A secondary key is a field that contains useful items of data often used in
searches. Unlike other keys, secondary keys are not always unique.
Relational databases
A relational database organises data using a series of related tables. Relationships
are built between the tables to provide a flexible way of manipulating and combining data. Forms are used to view, enter and change data in the tables. Relational
databases are the most commonly used database structure. The organisation of
data in a relational database involves a schema.
Schema
A schema (pronounced ‘skee-ma’) is the data definition for a database. It is an
organised plan of the entire database showing how and where the data is found,
descriptions of the data, and the data’s logical relationships. In a relational
database, the schema defines the entities, attributes and relationships:
• An entity is a specific thing about which information is collected and stored.
The School database has an entity for students, for teachers, for classes and for
students and classes (see Table 2.1). A flat file database would have a separate
file for each of these entities.
• An attribute is a defined property of an entity. The Students entity in the
School database has such attributes as LastName, FirstName and
PhoneNumber. Each attribute of the entity contains a data item. Attributes are
the same as fields in a flat file database.
• A relationship is the way the entities are related to each other. In the School
database, the entities are related using keys, such as StudentID. Entities are
related in three ways (see Figure 2.9):
– A one-to-one relationship occurs when each record in the first entity is
related to exactly one record in the second entity. For example, in primary
school each class has one teacher and each teacher relates to only one class.
As another example, only one customer purchases a new car, and the sale of
each new car is related to only one customer.
– A one-to-many relationship occurs when one record in the first entity is
related to many records in the second entity, but any record in the second
entity only relates to one record in the first entity. For example, one student
can take out many books from the library, but any one book can only be
taken out by one student at a time.
– A many-to-many relationship occurs when each record in the first entity is
related to many records in the second entity, and each record in the second
entity is related to many records in the first entity. For example, each
student studies many subjects, and each subject is studied by many students.
44
Core
Entity
Students
Attribute
StudentID
Table 2.1 Entities and attributes for the School
database.
FirstName
LastName
Address
Suburb
PostCode
PhoneNumber
Teachers
TeacherID
Teacher
PhoneNumber
Extension
Classes
ClassID
ClassName
TeacherID
Units
Students and Classes
StudentClassID
ClassID
StudentID
One-to-one
One-to-many
Student
Many-to-many
Student
Physics Class
IPT Class
Student
Student
Mathematics Class
Figure 2.9 A relational database can use three types of relationships.
45
A foreign key is an attribute (field) of a table that is a primary key of another
table. In the School database, the StudentID attribute is a foreign key of the
Students and Classes table and a primary key of the Students table. The data in a
foreign key of one table must match the data in the primary key of another table.
Tables
Information about an entity is displayed in a table. A table is the organisation of
data into columns and rows (see Figure 2.10). It is sometimes referred to as a
relation. A column of a table is also an attribute of an entity or a field of a record.
The data in a column must have the same data type and have a distinct name.
A row in a table is also called a tuple of an entity, or one record. Each row must
be uniquely identified by a key. The intersection of a row and column stores a
particular data item, such as ‘Rebecca’ in the first row and second column of the
School database. The rows and columns in a table can be viewed in any order
without affecting the contents of the table.
Attribute of the entity (field)
Tuple of the
entity (record)
Key field
Figure 2.10 Table from the School database.
Forms
Data is viewed for different purposes using forms. A form is used to view, enter,
and change data in a table (see Figure 2.11). The layout of the form can be
changed. The user can position fields, headings, instructions and graphics. A welldesigned form provides information explaining the required data and any dataentry rules that apply to particular fields. For example, the field name ‘Sex (M/F)’
leaves no confusion about what data is required and how it should be entered.
In a relational database, forms can be based on a single table or on multiple tables.
Figure 2.11 A form in the School database.
46
Core
Data modelling
Data modelling is the process of identifying entities, the relationships between
those entities and the attributes of those entities. It is used to develop a schema for
the database. Data modelling is critical to creating an efficient database. There are
a number of tools used for data modelling, such as data dictionaries, schematic
diagrams and normalisation.
Data dictionaries
A data dictionary is a comprehensive description of each field (attribute) in the
database. It contains information about the characteristics of each item entered in
the database, such as the field name, field size, data type and field description (see
Figure 2.12):
• Field name is the name of the field. It should be carefully selected to avoid
confusion. Field names should be relatively short but clear and unambiguous.
• Data type (or field type) is the kind of data that can be stored in the field. Each
field stores data in a single data type. Some common data types are text, memo,
number, currency, yes/no and date/time. Logical fields contain the logic values
‘true’ or ‘false’.
• Field size, or width, is the number of characters allowed in each field. It should
be limited to the smallest number of characters likely to be needed, as smaller
field sizes let the database work faster.
• Description specifies the contents of the field.
Figure 2.12 Data dictionary for the School database.
A data dictionary is a fundamental tool in the development of a database.
It consists of metadata, or information about data. It provides a common ground
for people working on a project at the same time. For example, if people are
47
working on different entities, they can refer to the data dictionary to check
whether a particular attribute already exists. This reduces data redundancy. Data
redundancy is the undesirable duplication of data within a database.
Schematic diagrams
Schematic diagrams are graphical tools that help define the database and develop
a schema. A common schematic diagram is called an entity-relationship diagram.
An entity-relationship diagram (ERD) is a graphical method of identifying the
entities and showing the relationships between them. It helps to determine the
data to be included in and excluded from the database. ERDs force people to have
a common understanding of the database. They are a useful tool to explain the
database. There are numerous notations for ERD. The ERD in Figure 2.13
represents an entity as a rectangle and uses lines to specify the relationships
between the entities.
Figure 2.13 An ERD generated from Microsoft Access for the School database.
Normalisation
Normalisation is the process of organising data into tables so that the results of
using the database are unambiguous and as intended. It is a refinement process
that aims to reduce data redundancy. Normalisation results in a database that is
more efficient but more complex because data is separated into more tables. For
example, Table 2.2 is used to keep track of customer purchases and the price of
the products. If you deleted a customer, you would also delete a price. Normalising
would solve this problem by dividing this table into two tables: a table about each
customer and a product they had bought and a table about each product and its
price. Making additions or deletions to either table would not affect the other.
48
Core
CustomerID
Product purchased
Price
929
IT Today
$50
970
Computers for dummies
$45
568
Access made easy
$60
Table 2.2 Customer table.
The degree of normalisation has been defined in terms of forms, such as:
• First Norm Form (1NF)—moving data items into separate tables where the
data in each table is a similar type. Each table is given a primary key. 1NF is the
basic level of normalisation and usually corresponds to the definition of a
database.
• Domain/key normal form (DKNF)—a key uniquely identifies each row in a
table. A domain is the set of permissible values for each attribute. Enforcing
key and domain restrictions ensures there are no problems when modifying the
database. DKNF is a final level of normalisation that most designers aim to
achieve.
Hypermedia
Hypermedia is a combination of media whose locations are linked electronically
to provide an easy way to navigate between the information. The information is
stored using a set of documents that may contain text, images, audio, video or
executable programs. Each document is independent, and information is retrieved
using hypertext. Hypertext is a system that allows documents to be cross-linked in
such a way that the user can move from one document to another by clicking on
a link. A link, or hyperlink, is indicated by a highlighted item (usually an underlined word or a graphic) that allows the electronic connection. The author of the
hypertext must specify the location of the information accessed by each link.
If another computer is the destination of the link, that computer is called a node.
The most well-known application of hypermedia and hypertext is the World Wide
Web. On the Web, each document is accessed through its uniform resource locator
(URL).
ITITFact
Fact
The Web is currently the largest index at over 200 million pages. Yahoo
employs over 150 editors and Web surfers to create its directories.
Uniform resource locator
A URL is the address of a file or resource on the Web. It is usually written in lower
case, as a single unbroken line, with no spaces (see Figure 2.14). The main parts of
the URL are the:
• protocol—the transfer method used to access a particular resource on the Web.
In most cases the protocol will be ‘http://’ (hypertext transfer protocol).
• domain name—address of the specific computer where the resource is located,
such as ‘www.hi.com.au’. The domain name can be replaced by the IP address.
49
http:// This stands for
hypertext transfer protocol,
which is the set of rules that
govern the transfer of data on
the World Wide Web. It indicates
that the resource is a Web page.
/atlas/ This indicates a directory
called ‘atlas’ within the Web site.
www This stands for the
World Wide Web.
http://www.hi.com.au/atlas/about.htm
hi.com This is known as the domain
name. It is usually made up of the name of
the organisation (hi for Heinemann
Interactive) and an extension that
indicates the type of organisation (in this
case ‘com’, which stands for ‘commercial’).
au This is a two-letter
extension that indicates the
country of the Web site (in
this case, Australia).Web
sites in the USA do not have
a country extension.
about.htm This is the file
name of an individual Web page
in the subdirectory.The extension
.htm stands for hypertext markup
language, which is the code used
to format all Web pages. Some
Web pages have a four-letter
extension (.html).
Figure 2.14 A uniform resource locator.
• file path—the full path to the file to be retrieved. It may be a simple filename,
or it may be a directory path, such as ‘atlas/about.htm’. The domain name and
the file path are separated by a forward slash (/).
URLs must be complete and exact; if they are not, the file or resource will not
be found. It is not necessary to memorise URLs. Web browsers have the ability to
store the addresses of Web sites. These stored URLs are called bookmarks or
favourites and can be organised into categories or folders to save you time.
Storyboard
A storyboard is a series of frames, each representing a different action or screen
image. It is a tool used to organise hypermedia. Storyboards are drawn on paper or
using a computer (see Figure 2.15). They are frequently edited. They define each
screen and its specific media type. Storyboards consist of navigation paths,
information and graphics. They are popular because they are simple to construct, are
easy to read and can be modified at every stage. There are four storyboard layouts:
• linear—a simple sequential path that is set up quickly
• hierarchical—a sequential path in a top-down design; the user starts at the
beginning and moves down through the multimedia product
• non-linear—no structure; the user moves between different layouts in any
direction
• combination—a blending of the above layouts.
50
Core
Figure 2.15 A storyboard layout.
HTML
Web pages are created using hypertext markup language (HTML). HTML is a set
of special instructions that indicate how parts of a document will be displayed and
navigated. HTML documents are actually text files that contain HTML
instructions. Many applications will save a document in HTML and insert the
special instructions. HTML documents are viewed in a Web browser.
An HTML editor is a software program that specialises in writing HTML code.
Instructions in HTML are given using HTML tags. HTML tags are metadata, or
information about data. A tag consists of a left angle bracket (<), a tag name and
a right angle bracket (>). Tags are usually paired, such as <H1> and </H1>, to start
and end the tag instruction. The end tag looks like the start tag except a slash (/)
precedes the text within the brackets. Every HTML document contains certain
standard tags, such as <head> and <body>. The <head> tag precedes the title and
the <body> tag indicates the beginning of the actual text (see Figure 2.16).
<html>
<head>
<TITLE> HTML </TITLE>
</head>
<body>
<H1>HTML document </H1>
<P>Welcome. This is a paragraph in HTML.
It is just text!</P>
<P>This is another paragraph in HTML.
HTML is easy.</P>
</body>
</html>
Figure 2.16 A basic HTML document.
51
Links are achieved using HTML’s hypertext-related tag. It is <A> and stands
for anchor. The document to be linked is specified using the instruction
HREF=“filename”. The filename refers to the location, or path, of the link. After
the hypertext reference, the text that will provide the link is specified. For
example, the format of a link is: <A HREF=“ipt.html”>technology</A>. The
hypertext reference is the document ‘ipt.html’, and the word ‘technology’ is
the hypertext link to this document. If the hypertext reference is in a different
folder or on another computer, its path must be specified. For example, the
format of a link to the file ‘ipt.html’ on the ‘hi.com’ computer is:
<A HREF=“http://www.hi.com/ipt.html/”>technology</A>.
Exercise 2.2
1 What are the advantages of computer-based databases over non-computer
databases?
2 Describe the data structure in a flat file database.
3 Explain the difference between a primary key and a secondary key.
4 What is a relational database?
5 Describe a schema.
6 List three ways entities are related.
7 What is data modelling?
8 What information is contained in a data dictionary?
9 What is the purpose of normalisation?
10 Explain the difference between a link and a node.
11 Describe the three parts of a URL.
12 What is a storyboard?
13 Describe HTML.
14 How are links achieved in HTML?
LEARNING ACTIVITIES
1 Investigate three different non-computer methods of organising data, such as
card files, filing cabinets and address books. How is the data organised? How is
the data stored? Who uses this method of organising data? Outline the
advantages and disadvantages of each method.
2 Find three different examples of non-computer databases in your home. For each
database, answer the following questions:
a What is the storage medium used for the data (what is the data stored in or
on)?
b How is the data organised?
c Is it possible to reorganise the stored data in a different way?
d Is it possible to maintain the database by adding, deleting or changing the
information?
3 The library uses a relational database to store information about borrowers and
books. Construct a schematic diagram to represent this existing system.
4 Stadium Australia has set up a booking system for all its events. The system uses a
relational database. There are three entities: Customers, Seats, and Events.
52
Core
– Customers: CustomerID, LastName, FirstName, Address, Suburb, PostCode,
Deposit and CreditCard.
– Seats: SeatNumber, EventID and CustomerID.
– Events: EventID, EventTitle, Date and Time.
a What would be the primary key for each entity? Give a reason for your answer.
b Create a data dictionary for this relational database.
c Create a schematic diagram for this relational database.
d Design a form for each entity that could be used for data entry.
e The date of birth is a useful piece of information about the customer. Add this
attribute to the database.
f Populate the database with dummy data. Save the database with the filename
STADIUM.
5 An organisation has a database that holds records of any gifts received from the
community during the year. The database is organised as follows:
– Person: PersonID, LastName, FirstName, Address, AmountToDate, and
DateLastGift.
– Gifts: PersonID, GiftDate and GiftAmount
a What attribute in the database is redundant? Give a reason for your answer.
b The manager of the organisation would like to personally thank all the people
who made a contribution to the organisation. He requires a list of supporters by
street and suburb. Modify the data structure so that this information would be
easily obtained.
c What would be the primary key for each entity?
d Create a data dictionary for this relational database.
e Create a schematic diagram for this relational database.
f Populate the database with dummy data. Save the database with the filename
GIFTS.
6 Max Music is a small business that offers an online ordering service for its
customers via the Internet. It wants to expand its Web site by adding Web pages
to display the latest music releases. Each new Web page should contain
information about one CD, such as the artist, type of music, background, date
released and a description. Construct a hypertext document from a storyboard for
these Web pages. Each Web page should be linked.
2.3 Storage and retrieval
People need secure and efficient methods for storage and retrieval of information
from a database. The tool used for this purpose is called a database management
system.
Database management systems
A database management system (DBMS) is a software package that allows users
to access a database so they can enter, maintain and view the data. The terms
database and DBMS are often used incorrectly. A database contains the data, and
the DBMS provides access to this data. The data is independent from the DBMS.
In a DBMS, data is organised into tables, viewed in forms, retrieved using queries
and displayed in reports. A DBMS manipulates the data in many different ways,
such as sorting and searching. It also performs a number of tasks to help users
develop and maintain a database, such as:
53
•
•
•
•
•
•
organising the data using a data dictionary
showing relationships between entities using schematic diagrams
checking for identifiable errors in data entry
allowing flexibility to change the definition of the database
restricting access to the data to authorised people (see Figure 2.17)
providing information about the performance of the database.
Figure 2.17 Restricting access to a database.
Methods of accessing data
Sequential and direct access are two methods of accessing data.
Sequential access occurs when data is accessed in a sequence. It is the only
method of accessing data stored on magnetic tape. Data on a magnetic tape is
retrieved by starting at the beginning of the tape and reading all of the data until
the required item is found. Sequential access processes data in the order it was
stored. It does not require the exact location of the data item. Sequential access is
much slower than direct access and impractical when immediate processing is
required.
Direct access occurs when data is accessed without accessing previous data
items. Data is stored in a particular storage location based on a mathematical
procedure or algorithm. Direct access uses this algorithm to calculate the
approximate location of the data. If the data is not found at this location, the
computer searches through successive locations until the desired data is accessed.
Direct access often involves the use of an index and is then called indexed access.
An index is a table that contains information about the location of the data. Data
is accessed by referring to the index and obtaining the exact location of the data.
Indexed access requires additional processing time to search the index and to
maintain the index. The indexed access method is widely used to store data on a
disk, as well as to store the logical location of data within a database.
Distributed databases
A distributed database is a database located at more than one site. It acts as a
single collection of data but is geographically dispersed. Distributed databases
reduce the data transmission costs that would occur if all users at all sites had to
access one centralised database. However, a distributed database makes it more
difficult to obtain a complete view of the database.
Distributed databases often need to be synchronised to keep them current.
Consider a distributed database with part of the database at a warehouse and
54
Core
another part at head office. If the office staff place an order from the warehouse,
then both parts of the database need updating. This may create a problem if an
error occurs in transmission and only one part of the database processes the
transaction. A two-phase commit is part of the DBMS used to maintain consistency across a distributed database. It checks whether both parts of the database
are ready for the transmission and then performs the transmission.
Storage media
Storage of data is online or offline. Online storage uses a peripheral device that is
under the user’s direct control, such as a hard disk on a personal computer. Offline
storage uses a peripheral device that is not under the user’s direct control, such as
a centralised database. Both online and offline storage use a variety of peripheral
devices and storage mediums:
• A hard disk is a disk made of metal or glass and covered with magnetic
material. Hard disks are usually mounted inside the computer’s case (fixed),
and their storage capacity is usually measured in Gb. Magnetic disks use direct
access to retrieve data.
• An optical disc is a polycarbonate plastic disk with a reflective layer of metal
covering the surface. Data is read and written using laser technology. Optical
discs use direct access to retrieve data. There are many kinds of optical discs,
such as compact disks with read-only memory (CD-ROMs) and digital
versatile disks (DVDs):
– CD-ROM disks are 12 centimetres wide and capable of storing 650 Mb.
They are convenient for storing data that remains constant, such as
encyclopedias.
– DVD is a disk format that can store large amounts of data. A DVD-ROM
is the same physical size as a CD-ROM but provides storage of 4.7 Gb
to 17 Gb.
• A removable cartridge is a hard disk encased in a metal or plastic cartridge and
can be removed like a floppy disk. Removable cartridges are fast, though
usually not as fast as fixed hard disks, and use direct access. There are two
common types of removable cartridges:
– Zip disks (or cartridges) store 100 or 250 Mb of data and have a transfer rate
of 1 Mb per second.
– Jaz disks (or cartridges) are an upgrade of the Zip disks. They store up to
2 Gb of data and have a transfer rate of 5.5 Mb per second.
• A magnetic tape is a very long, thin strip of plastic, coated with a thin layer of
magnetic material. The tape is wound on two reels inside a cartridge. Magnetic
tapes can store large quantities of data inexpensively and are often used as a
backup medium. They use sequential access to retrieve data.
Encryption
Encryption is the process of encoding data, and decryption is the process of
changing it back (decoding). It is the most effective way to achieve data security
during the transmission of data. Data is encoded, transmitted, and then converted
back to its original form. Encrypting data is essential for transferring financial
transactions and is used extensively on the Internet. Encryption methods often
involve complex manipulations of bit patterns. One problem with encryption is to
find a method that is difficult to decode but is also practical to use. There are two
main types of encryption:
55
• Asymmetric encryption requires a key for encryption and a key for decryption.
A common asymmetric encryption system is public key encryption. It involves
a public key that is widely available and a private key that is kept secret. Both
keys are developed using complicated number theory. The public key is used to
encrypt the message before it is transmitted, and the private key is used to
decrypt the message when it is received.
• Symmetric encryption requires the same key for both encryption and
decryption. A common symmetric encryption system is the Data Encryption
Standard (DES).
ITITFact
Fact
Whitfield Diffie and Martin Hellman invented public key cryptography in
1976. For this reason, public key encryption is sometimes called DiffieHellman encryption.
Backup and security
If the computer goes down or the storage media or database is damaged, the costs
of interrupted operations and replacing any lost data can be enormous. A DBMS
contains backup and recovery capabilities to guard against data loss. A backup is
another copy of the data that can be used to rebuild the system. A DBMS creates
a backup at a specified time. If the system goes down, the recovery process
rebuilds the data. It uses the last completed backup and a journal listing all the
actions completed by the DBMS since the last backup. The success of backup and
recovery depends on implementing appropriate procedures. Backups are usually
stored offsite or in a fireproof safe.
Security is another important database
issue. Data can be stolen, destroyed or
maliciously modified. There is a greater
risk when the data is accessible to
multiple users over a network. Data
security involves a series of safeguards to
protect the data. The first line of defence
is to only allow access to data by
authorised people using passwords,
personal objects and biometric devices.
However, some people are capable of
evading these procedures. Further safeguards to protect data involve data
encryption and firewalls. A firewall can be
used on the Internet or on any network to
verify and authenticate all incoming data.
It checks the password of anyone trying
to access the network. Firewalls are
expensive to install and maintain. On
large systems, more than one firewall is
necessary because barriers need to be
placed at all critical points.
56
Core
Sorting
Database information is always easier to use when data is arranged in a meaningful
order rather than randomly as it was entered. Sorting is the process of arranging
data in a particular order. Sorts are performed in either ascending or descending
order. Ascending order arranges data from smallest to largest (for example, 0 to 9)
or from first to last (for example, A to Z). Descending order is the reverse, from
largest to smallest (9 to 0) or from last to first (Z to A). Sorting can be done on
more than one field (attribute) so that records are arranged in the most useful
order. For example, Figure 2.18 shows the School database sorted on two levels,
with Last Name being the primary sort field and First Name the secondary
sort field.
Figure 2.18 The School database sorted on two levels.
Searching
Data needs to be quickly and efficiently retrieved from a database. Searching is
the process of examining the database to retrieve data. An effective search in a
small database may involve browsing a table or using the Find or Search
command. However, in a large database, the most efficient way of searching is to
construct a query.
Querying
A query is a search of a database for records that meet a certain condition. It is a
question you ask of the database. For example, what is the name of the student
who lives at ‘4 Beach Rd’? The results of a query are usually displayed in a table
but can be used as the basis of a form, report or graph or even another query. A
query can also update or delete multiple records at the same time and perform
built-in or custom calculations on data.
A query is constructed in the form: <Field name> <Operator> <data>. The
data in the query is often called the criteria. For example, if the Information
Processes and Technology class from the School database was required, the query
would be in the form ‘ClassName = Information Processes and Technology’. A
common method for constructing a query is query by example (QBE). It requires
the user to enter the criteria against a field. For example, in Figure 2.19, the
criteria ‘Information Processes and Technology’ is entered underneath the
ClassName field. If the search of a database involves two or more entities, it is
called a relational query.
57
Figure 2.19 A query by example on the School database.
Operator
Description
Relational Operators
=
Equal to
<>
Not equal to
<
Less than
>
Greater than
<=
Less than or equal to
>=
Greater than or equal to
contains
does not contain
begins with
ends with
is blank
is not blank
Logical Operators
AND
both
OR
either one
NOT
exact opposite
Table 2.3 Examples of operators.
58
Core
Operators
Some queries are constructed using an
operator, such as those in Table 2.3. The
operator represents the action to be
performed in the query. Operators
are classified as either relational or logical.
Relational operators (=, <>, <, >,
<=, >=) are characters or symbols
indicating the relationship between two
expressions. Wildcard characters represent
one or more unknown characters. Some
common wildcard characters are the
asterisk (*), which substitutes for any
number of characters, and the question
mark (?), which substitutes for one
character. The query ‘LastName = Ma*’
would find such last names as Mat, May,
Madrid and Martinelli. However, the query
‘LastName = Ma?’ would only find such
last names as Mat and May.
Logical operators (AND, OR, NOT) are used to combine queries so that a
search is carried out on one or more fields. It is important to understand the
difference between the AND and OR operators:
• The AND operator requires both the first and the second query to be true. It
retrieves records that satisfy both queries. For example, if you require data
about a student with the last name Howe who lives in Kearns, the query would
be: ‘LastName = Howe’ AND ‘Suburb = Kearns’.
• The OR operator requires either the first or the second query to be true. It
retrieves records that satisfy either of the queries. For example, if you require
data about all of the students with the last name Howe and all the students
who live in Kearns, the query would be: ‘LastName = Howe‘ OR ‘Suburb =
Kearns’.
SQL
A query language is a specialised language designed to search a database. There
are different query languages, each with its own grammar, syntax and vocabulary.
Structured Query Language (SQL and pronounced ‘see-qwell’) is a query
language used to access and manipulate data in a relational database. Variations to
SQL have been developed by specific DBMSs. However, most of these variations
are extensions to ANSI SQL, or standard SQL.
ITITFact
Fact
SQL grew out of research on relational database models conducted by IBM
in the 1970s. It developed from Structured English Query Language
(SEQUEL). For this reason, the pronunciation of SQL is ‘sequel’ and
not ‘squeal’.
SQL statements contain keywords that are used to perform a particular task.
For example, the select statement is used to query the database and retrieve
selected data that matches the criteria. A simple select statement may contain the
keywords SELECT, FROM, WHERE and ORDER BY (see Table 2.4).
Keyword
Values
Description
Example
SELECT
Field(s)
The data to be displayed
SELECT FirstName,LastName
FROM
Table(s)
The source of the data
FROM Students
WHERE
Search criteria The query
WHERE LastName = “Mullins”
ORDER BY
Field(s)
ORDER BY LastName DESC
The order in which the results
are to be displayed
Table 2.4 Keywords used in a simple SQL select statement.
59
When searching in SQL, it is essential to use the correct syntax. In most
DBMSs, the keywords are written in upper case, the fields are separated by
commas, an entity and an attribute in that entity are separated by a full stop, and
the search criteria or data item is enclosed in double quotes. The keyword
ORDER BY sorts on a field in ascending (ASC) or descending (DESC) order.
Ascending order is the default and can be omitted. The SQL query in Figure 2.20
is the same as the query in Figure 2.19 that was developed using QBE.
Figure 2.20 A SQL query on the School database.
Hypermedia and searching
Data is retrieved from a database using the data structures and the relationships
between entities. The process of retrieving data in hypermedia is completely
different. It involves using search engines.
Search engines
A search engine is a database of indexed Web sites that allows a keyword search.
An index is a table that contains information about the location of data. A search
engine’s index is built by regularly scanning the Web for new sites and accepting
submissions from Web page authors. The scanning is often completed by programs
called spiders, crawlers or robots. They send back the URL of any document they
find to the search engine’s indexing software (see Figure 2.21). This indexing
software collects information, such as titles and keywords, from the Web sites,
then indexes these words in a database. Each search engine has a different method
of building its index; this is why you often obtain different results from the same
keyword search when you use a different search engine.
Indexes allow documents to be found using a keyword search. A keyword is
entered related to the topic of interest. Most search engines allow a search on a
series of keywords and for specific information. When the user requests a keyword
search, the search engine scans the index for the keywords and lists the Web sites
that contain those keywords. Choosing the right keyword is crucial to the success
of a search. In general, use more than one keyword such as synonyms and select
keywords that are very specific. Search engines allow the use of Boolean qualifiers,
such as ‘AND’, ‘OR’ and ‘NOT’ to refine a search.
60
Core
WORLD
WIDE WEB
YOUR
COMPUTER
1
SEARCH
ENGINE
3
Database
2
URLs
Keywords
URLs
4
1 Spiders follow hyperlinks on the World Wide Web
2 The spider sends back URLs to the search engine’s indexing software
3 You conduct a keyword search
4 A list of URLs for Web pages containing these keywords is returned to
your computer
Figure 2.21 How a search engine works.
Some search engines offer directories. Directories are lists of Web sites
organised into categories, such as computers, games or sport (see Figure 2.22).
They are another way to find information on the Internet. The owners of a Web
site have to register their site to be included in a directory. As a result, directories
cover only a small fraction of the pages available on the Web. A directory is useful
for finding information on a general topic.
Figure 2.22 Directories at AltaVista.
61
A search robot is a program that accesses Web sites and gathers information
for search engine indexes. AltaVista has a search robot called Scooter. It asks each
server which files should be excluded from being indexed, it does not go through
firewalls, and it uses a special algorithm so that response time for other users is
not affected.
Exercise 2.3
1
2
3
4
5
6
7
8
9
10
11
12
13
Explain the difference between a database and a DBMS.
Describe accessing data using an index.
What is a distributed database?
Briefly describe some of the storage media used by information systems.
What is public key encryption?
Describe the process of backup and recovery.
Explain the difference between searching and sorting.
What is QBE?
List four keywords in SQL and describe their purpose.
How is a search engine index built?
Describe a search engine that offers directories.
What is a search robot?
Write the meaning of the following queries:
a Class = 12*
b Postcode = 261?
c LastName begins with H
d Assessment > 60
e FirstName = “Peter” AND Suburb = “Mossman”
f Colour = “Red” AND Cost > $500
g LastName = “Tran” OR PostCode = “2534”
h StreetNumber = “9” OR Price < $500
14 Write out queries using relational operators for each of these searches:
a Year 12 boys in the school.
b Borrowers who live in either Auburn or Lidcombe.
c Girls in the netball club who are eligible to play in 18 and under teams.
d All customers who owe more than $10 000 for the month of July.
15 The following questions refer to the School database in Figure 2.18.
a Write down the StudentID of the second record if sorted on ‘FirstName’ in
ascending order.
b Write down the StudentID of the third record if sorted on ‘Phone Number’ in
descending order.
c Which of the ‘Mullins’ would come first if the primary sort field was ‘LastName’
and a secondary sort field was ‘StudentID’?
d Write down the StudentID of the first record if the primary sort field was
‘Address’ and a secondary sort field was ‘StudentID’?
62
Core
LEARNING ACTIVITIES
1 Melissa Harris has decided to organise a small bus service. She has constructed a
database using the following data structure:
– Bus: RegistrationNo, PeopleCapacity, Model, Colour and Details
– Patron: PatronID, FirstName, LastName, Address, Suburb and Postcode
– Job: JobNumber, PatronID, RegistrationNo, AmountReceived and Destination.
Create a data dictionary and an ERD for this database. Populate this database with
dummy data. Save the database with the filename SMALL BUS. Construct the
following queries:
a All the buses with a capacity greater than 8 people.
b All the buses whose model is a type of Toyota.
c All the patrons whose last name starts with the letter ‘S’.
d All the patrons whose address is in a street.
e All the jobs where the amount received was greater than $40.
f All the patrons where the amount received was less than $50.
g All the jobs that used a Toyota bus or whose destination was Sydney.
h All the patrons who travelled in a red bus and whose address contains the
letter ‘a’.
2 A retail organisation keeps data about its employees in a database:
– Employee: EmployeeID, LastName, FirstName, Address, Suburb, PostCode, and
Department
– Wage: EmployeeID, WeeklyPay, PayDate and WeeklyTax
a Describe the results of this SQL query:
SELECT FirstName, LastName
FROM Employee, Wage
WHERE Employee.Department = “Sport” AND Wage.WeeklyPay > 1000
ORDER BY LastName
b Describe the results of this SQL query:
SELECT EmployeeID
FROM Employee, Wage
WHERE Employee.Suburb = “Cabramatta” OR Wage.PayDate = #31/07/01#
ORDER BY LastName DESC
c Construct a SQL query that could be used to retrieve the name of all employees
who work in the office and live at either Ryde or Hunters Hill.
d Construct a SQL query that could be used to retrieve the name and address of
all employees whose weekly tax is less than $50 on 12 August 2001.
e Create a data dictionary and an ERD for this database. Populate this database
with dummy data. Save the database with the filename RETAIL. Verify your
answers to the queries in questions (a) to (d).
3 The Internet has many large databases that can be accessed using a keyword
search. Use your Web browser to access the following Web sites. Describe the
information that can be obtained from each site.
a http://www.whitepages.com.au
b http://www.hoyts.com.au
c http://www.tradingpost.com.au
4 Find information about databases on the Web by using more than one search
engine. Create a list of sites and their URLs that you found useful. Compare your
list with another student in your class. Rank the top three sites from both lists.
Compare these lists as a class. What are your class’s top three sites?
63
Displaying is presenting the output from an information system or database to
meet a given purpose. The presentation of information could be in the form of
text, numerals, images, audio or video. A report is one way to display information
from a database.
Reporting
A report is the formatted and organised presentation of data. Examples of reports
are mailing labels, invoices, sales summaries and telephone lists. A DBMS allows
complete control in the design of a report in either a tabular layout (displays data
with the fields extending across the page) or a column layout (displays data with
the fields going down the page). It is possible to insert headings, sort data, choose
the fields, switch fields, change column widths and select records. The purpose of
the report determines its content, format and style. Most DBMSs allow different
reports to be created from the database for different purposes (see Figure 2.23).
Figure 2.23 A report from the School database.
Before creating a report, the user needs to select the required records by
constructing a query. For example, you may not need a mailing label for everybody
in the School database. Reports are often based on a query. The next step in
creating a report is to select the fields. These fields are placed in appropriate
positions, formatted, and sorted. DBMS reports often offer such functions as
count, sum, and average to perform calculations on selected fields. Most DBMS
reports have the following sections (see Figure 2.24):
64
Core
• The report header appears once at the beginning of a report. It contains such
items as a logo, report title and date.
• The page header displays information such as a title, column headings, or any
information needed at the top of every page. A page header appears after the
report header on the first page of the report.
• The details section displays most of the information. The user has a variety of
tools to manipulate and format fields.
• The page footer displays information such as the date, page number or any
other information the user wants at the bottom of every page.
• The report footer appears once at the end of the report. It displays items such
as report totals. The report footer appears after the page footer on the last page
of the report.
Figure 2.24 Designing a report for the School database.
Constructing different views
Different views of a database are obtained using a form. A form is used to view,
enter, and change data in a table. The layout of the form can be changed. The
user can position fields, headings, instructions and graphics on the form. A
well-designed form provides information explaining the required data and any
rules that apply to particular fields. Forms are used to display information for
different purposes.
Before selecting the ‘Print’ command to send the report to the printer, make
sure the report has the correct format. When formatting a report, the user needs
to adopt good design principles, such as:
• headings that identify the purpose of the report
• layouts, such as tabular or column, that efficiently present the information
• text that is balanced on the page either vertically or horizontally
• styles that are consistent throughout the report and with its purpose
• columns that have clear and descriptive headings
• white space that is appropriately used to improve readability
• page numbers and the date included in the header or footer.
65
ITITFact
Fact
Stickiness is the quality of a Web site that induces visitors to remain on the
site rather than move to another site. It is the length of time a visitor accesses
a site. Stickiness is a valuable measure for convincing advertisers to
patronise a site.
Case study
Roads and Traffic Authority
The Roads and Traffic Authority (RTA) is
an organisation that uses a database
information system. Its purposes are to
ensure vehicles are safe and to provide
individuals with a driver’s licence. The
environment of the RTA is not only its
offices throughout New South Wales but
also such factors as communications,
insurance cover, police records and the cost
of new vehicles. The RTA performs a set
of information processes that requires
participants, data/information and information technology (see Figure 2.25).
When the owner of a vehicle needs to
renew the registration, he or she requires a
pink slip and a green slip. This data is
presented at one of the RTA offices. A
central database is used to store the details
of each vehicle, such as plate number,
model and engine number. The owner pays
the registration and presents the pink and
green slips. This data is automatically
updated using offline storage. An entity
also exists to store information about
holders of driver’s licences, such as their
licence number, address and expiry date.
Purpose
• Ensure vehicles are safe
• Protect road users
• Collect pink/green slips
• Search database
• Update database
• Print details on rego form
Participants
Data/
Information
Information
Technology
• Manager
• Owner data
• Terminals
• Staff
• Pink slip
• Central computer
• IT personnel
• Green slip
• Database
Information System
Figure 2.25 Registering a vehicle at the RTA.
66
Core
Figure 2.26 RTA’s Web site.
This information is also updated at RTA
offices. Information about registration of
vehicles and obtaining a driver’s licence
is obtained from the RTA Web site (see
Figure 2.26).
The participants of the RTA are continually carrying out the information
processes. These processes are not completed in any order. The staff can move
from collecting the data to displaying the
information. The information processes
include:
• collecting—entering data from pink
and green slips
• organising—searching the database for
owner details
• analysing—determining the type of
information required
• storing and retrieving—saving and
backing up the database
• processing—updating the information
in the database
• transmitting and receiving—transferring the data between terminals and
the central computer
• displaying—printing details on the
registration form.
Figure 2.27 An ERD for the RTA, showing entities, attributes and relationships.
67
Exercise 2.4
1
2
3
4
5
6
7
What is a report?
List some examples of reports.
Why is a report often based on a query?
List the sections of a report.
Explain the difference between a report header and a page header.
What is usually displayed in a report footer?
The following questions relate to the RTA case study:
a What are the purposes of the RTA?
b Describe the participants, data/information and information technology.
c List the data in the registration table.
d List the data in the driver’s licence table.
e Describe the information processes at the RTA.
LEARNING ACTIVITIES
1 In the RTA case study, a relational database was used to organise and store data.
Create a data dictionary and an ERD for this database. Populate this database with
dummy data. Save the database with the filename RTA.
a Create a report to display all the registration information. The report should be
sorted on expiry date in ascending order.
b Create a report to display all the driver’s licence information. The report should
be sorted on expiry date in ascending order.
2 St Peters High School is using a relational database to store student data. A
portion of the database involves the following three entities:
– Students: StudentID, FirstName, LastName, Address, Suburb, Postcode, Date of
Birth and Gender
– Contact: StudentID, FirstName, LastName, Address, Suburb, Postcode,
MailingName and ContactPhone
– School: StudentID, SportHouse and Subjects
Create a data dictionary and ERD for this database. Populate this database with
dummy data. Save the database with the filename ST PETERS.
a Create a report that lists all the male students. The report should display the
students’ first name, last name and gender. It should be sorted on last name in
ascending order.
b Create a report that lists all the students who are in a particular sports house.
The report should display the students’ first name, last name and contact phone
number. It should be sorted on contact number in descending order.
c Write a letter using a word processor advising the contact person about some
proposed changes to the school this year. Insert merged fields from the
database into the letter. Merge the letter and the database so that each person
receives a personalised letter. Create mailing labels for each letter, using the
database.
68
Core
2.5 Issues related to information
systems and databases
Both positive and negative impacts arise from the introduction of information
systems and databases. In this section, we examine some of the social and ethical
issues raised by information systems.
Data source
The source of the data is the person or organisation that developed the data. Data
may come from informal sources, such as a conversation, meeting or observations.
It may also be obtained from formal sources, such as a report, book or official
document. A formal source often provides data that is logically organised.
However, this is no guarantee to its accuracy. The source of the data is protected
by the Copyright Act. People are not allowed to copy the work of another person
without permission. It is against the law to violate copyright.
Most data obtained from the Internet is protected by copyright. Text and
images obtained from a Web site should not be used without acknowledgment of
and permission from the owner. However, the Copyright Act does make special
provisions for students to use information for research purposes. It allows students
to use a reasonable portion of the original work if the work is correctly cited. To
cite an Internet source, include the following information: author’s surname and
initial or organisation’s name, title of the complete work or Web page, URL of the
Web page, date of the document or Web page publication, and the download date.
Accuracy of data
Accuracy of data is the extent to which it is free from errors. Data that is collected
on individuals is not always accurate. The inaccuracies may be caused by mistakes
in gathering or entering the data, by a mismatch of the data and the person, or by
out-of-date information. For example, a car recorded as stolen is later recovered
and returned to the owner. If the data has not been quickly updated, the legal
owner runs the risk of being arrested as a car thief. Opportunities to check and
change incorrect data need to be provided. It is often necessary to compare data
from a number of different sources to determine which data is accurate.
Data validation is used to check the entry of data:
• A range check is used if the data is restricted to a small range of particular
values. For example, when the data is entered in the format dd/mm/yyyy, a
range check could be used to determine whether the first two digits are in the
range of 1 to 31 and whether the second two digits are in the range of 1 to 12.
• A list check is used when the data can be compared to a set of accepted data.
For example, when the data entered is an Australian state, then NSW would
be accepted but not NSX.
• A type check is used to determine whether the data type is correct (see Figure
2.28). For example, when the data is entered for a person’s family name the
software will check whether the data is text. It would not accept a ‘date’ for a
person’s name.
• A check digit is a digit calculated from the digits of a code number and then
added to that number as an extra digit. For example, the ISBN number
0 85859 921 319 4 has a check digit of 4, and the check digit is calculated from
0 85859 921 319.
69
Invalid data type
Figure 2.28 Data validation rules.
Data integrity describes the reliability of the data. Reliable data is accurate,
current and relevant. There is no guarantee that data received from the Internet is
reliable. It is easy to publish information on the Internet. Organisations that are
not the creators of the information often provide access to it. Who is responsible
for the accuracy of the information? Is the creator the only person responsible for
the accuracy of the data? Do organisations that provide access to information have
a responsibility to verify its accuracy? Clearly it is necessary to compare data from
a number of sources and to determine which data is accurate.
ITITFact
Fact
A ghost site is a Web site that is no longer maintained but that remains
available for viewing. It is often difficult to identify ghost sites, as many Web
sites do not display the date of the last update.
Privacy
Privacy is the ability of an individual to control personal data. It is a major concern
for those involved with databases and their use. Large organisations, such as banks,
use databases to store information about their customers. This information is
confidential. It should not be used for other purposes or be made available to
anyone outside the organisation. Privacy is also eroded by linking databases. People
leave a trail of electronic data when they use a credit card, visit the doctor, use the
library, access the Internet or subscribe to a magazine. If this data was combined,
it could create a fairly detailed picture of a person.
Access to data
Access to data is the extent data is available to people. Should all information be
free and available to all? What kind of access should individuals have to
information about themselves? Why can’t people have free access to data about
themselves located in business databases? Do people have the right to access and
check their credit history or medical data? The Freedom of Information Act is
70
Core
designed to allow individuals to find out what data is being kept by the
government and other public bodies. It states that individuals have the right to
access information where it relates to the individual and does not invade another
person’s privacy. There is a fee for the release of this information (see Figure 2.29).
However, knowing what data is being kept does not indicate how it will be used.
Figure 2.29 Web site for Freedom of Information Act.
People can use our preferences, weaknesses and habits to their advantage. That
is, data on what we buy, how we pay for it, what we read, what we watch on
television and how much we earn is valuable data for those who want to sell us
things. Ownership and control of this data is an ethical issue. Who owns this data?
Is it the individual, or is it the organisation that has processed the data? Is the data
being combined, sold and exchanged? For example, an application for an
extension to a house is sent to the local council for approval. Who owns this data?
Does the building inspector have the right to sell this processed data to a
bricklayer? On the other hand, might the owner of the house appreciate another
quote for laying bricks?
Data warehousing and data mining
A data warehouse is a database that collects information from different data
sources. It is a storage area of raw data that can be analysed to assist organisations
to make decisions. A data warehouse involves careful planning to decide what data
to collect. The contents of a data warehouse are usually historical and static.
However, they will change if new requirements are identified. A more
sophisticated approach to obtaining information is to use data mining.
Data mining is a process that looks for relationships and patterns in the data
stored in a database. It sorts through the data and turns up interesting and useful
connections. For example, data mining could be used to analyse the transactions at
a supermarket. It might determine that there was a relationship between tomato
sauce sales and meat pie sales. This information might be useful for marketing
promotions. One problem with data mining is that many of the patterns occur by
chance and have no value in making decisions. It also raises issues of privacy and
ownership of data.
71
Exercise 2.5
1
2
3
4
5
6
7
8
Explain the difference between an informal and a formal source of data.
How do you cite an Internet source?
How is inaccurate data obtained?
List four methods of validating data.
Describe a range check.
Why is privacy a major concern?
What is the purpose of the Freedom of Information Act?
Describe a problem with data mining.
LEARNING ACTIVITIES
1 A flat file database is used by a school for student records. There are separate files
for student data, financial data, teacher data and assessment results. A relational
database has been suggested to the principal as a better system. Outline the
advantages of a relational database over a flat file database. Your answer should
contain references to data accuracy, data redundancy, security and development
time.
2 Privacy and access to data are two important issues related to databases. Consider
a student database containing name, address, gender, ethnicity, family, financial
status, health, discipline record and assessment results. Should access to this data
be given to the student, other students, teachers, the department of education,
potential employers or other organisations? Is there a need to provide some
groups with limited access? Explain your answers.
3 ‘Databases should not have the same copyright protection as books and software.’
Do you agree with this statement? Give reasons for your view.
4 Max Music is a small business that offers an online shopping service for its
customers via the Internet. Customers place orders for CDs using their credit card
and register preferences for categories of music. This data is stored in a database.
Research indicates that preferences for music are also a good indicator for book
and video preferences. Describe the ethical issues raised if Max Music sells each
customer’s preferences to a book company?
72
Core
Chapter review
PART A
1 The main advantage of a computerbased database compared to a paper
filing system for retrieving information
is that the:
A data can be searched more efficiently
B data is very accurate
C storage medium is a hard disk
D data is organised into data structures
2 What is the specific thing about which
information is collected and stored in a
relational database?
A file
B record
C entity
D schema
3 A single key that must have a unique
value and is used to sort and retrieve
information:
A secondary key
B primary key
C composite key
D foreign key
4 A storyboard layout that has no
structure is called:
A linear
B hierarchical
C non-linear
D combination
5 Metadata is contained in a:
A data dictionary
B data record
C hyperlink
D primary key
6 A customer file contains an identification number that is linked to a
transaction file. This is an example of a:
7
8
9
10
A hypertext link
B record
C key
D column.
The video staff wish to retrieve information from the membership file
about borrowers whose first name is
‘Ann’ with a post code of ‘2176’ who
borrowed movies starring ‘Cary Grant’.
A FirstName = “Ann” OR PostCode =
“2176” OR Mainstars = “Cary Grant”
B FirstName = “Ann” AND PostCode =
“2176” OR Mainstars = “Cary Grant”
C FirstName = “Ann” OR PostCode =
“2176” AND Mainstars = “Cary Grant”
D FirstName = “Ann” AND PostCode =
“2176” AND Mainstars = “Cary Grant”
Metadata is used in the organisation
and retrieval of data. One example of
metadata is the:
A records stored in a database.
B tables used to organise data into
rows and columns.
C HTML tags used to create Web pages.
D search engines used to retrieve data
from the Web.
A query uses a wildcard to search a
database in the form FirstName =
“M?c*”. Which of the following would
not be retrieved?
A Michael
B Mick
C Mac
D Mitchell
The reliability of the data in a database
is called:
A data security
B data redundancy
C data integrity
D data validation
73
Chapter review
PART B
statement number.
Statements
1 A database that organises data using a
series of related tables.
2 A query language used to access and
manipulate data in a relational database.
3 The address of a file or resource on the
Web.
4 Data accessed without accessing previous data items.
5 The data definition for a database.
6 A field that is used to sort and retrieve
information.
7 A comprehensive description of each
field in the database.
8 A formatted and organised presentation of data.
9 A technique to reduce data redundancy.
10 A system that allows documents to be
cross-linked.
11 Data accessed in a sequence.
12 A search of a database that meets a
certain condition.
List of terms
a data dictionary
b direct
c hypertext
d key
e normalisation
74
Core
f
g
h
i
j
k
l
query
relational
report
schema
sequential
SQL
URL
PART C
following questions.
1 What is hypermedia? How are documents created on the Web?
2 Explain the difference between the
following terms:
a schema and data dictionary
b data validation and data redundancy.
3 What is a DBMS? Outline some its functions.
4 Explain the difference in organisational
methods between a flat file database
and a relational database.
5 Describe a method of identifying entities and showing their relationships.
6 Outline two methods for constructing a
query.
7 Describe the process of retrieving data
using a search engine.
8 Identify a social or ethical issue involved
in keeping data about individuals in a
database. Briefly explain how the rights
of the individual can be protected in
this case.
3
chapter
C O M M U N I C AT I O N
SYSTEMS
Outcomes
processes (H3.2)
Overview
This chapter features the information processes
of transmitting and receiving using communication systems. You will learn the characteristics
of communication systems and some of their
applications. The chapter provides a comprehensive understanding of networks and the
issues related to communication systems.
3.1 Characteristics of
communication systems
A communication system enables people to send and receive data and
information. We depend on communication systems. The telephone, radio and
television are examples of communication systems that have had a dramatic
impact on our society. All communication systems have five basic components:
1 The data source produces the data to be sent.
2 The transmitter encodes the data into a signal suitable for a transmission
medium.
3 The transmission medium is a channel, such as a cable, in which the signal is
transmitted to the destination. The signal may be changed or distorted during
transmission.
4 The receiver decodes the signal back into the original data or an approximation
of the data.
5 The destination is the receiver of the information.
These components can be applied to any communication system, such as the
radio. In radio, the data source is the person speaking into the microphone. The
transmitter is the microphone and associated electronics that change the sound into
a signal. The transmission medium, or channel, is the space between the transmitting
and receiving antennas. The receiver is the radio that converts the signal into the
original sounds, and the destination is the person listening to the radio.
Communication systems are used in information systems when participants
need to transmit and receive data and information. When people withdraw money
from an ATM, they are accessing an information system and using a communication system (see Figure 3.1). Data and information are being transferred
between an ATM terminal and the bank’s central computer. When computers
and other devices are connected in some way like the ATMs, they form a network. In this topic, we are focused on communication systems that involve a
network.
Good communication systems have
an accurate, reliable and secure transmission medium. They should also have
a minimum delay in communicating.
Good communication depends on protocols, handshaking, speed of transmission and error checking. These factors
depend on the information technology
used in the communication system.
Figure 3.1 ATMs are part of a communication
system.
76
Core
Protocols
Communication systems need protocols for communication. A protocol is a set of
rules that governs the transfer of data between computers. It defines how the
information is transmitted and how the errors are detected. Two computers must
use the same protocols when they are communicating; otherwise, the data transfer
may be unsuccessful. The standardisation of data communication protocols has
been the focus of a major international effort over many years. Protocols are
written into internationally accepted standards, such as the OSI reference model.
The OSI reference model divides data communication into seven layers. Each
layer expresses the standard, using a protocol. The bottom layers are responsible for
transfer of data from one place to another. They include protocols that specify the
type of plugs, the format of data, the method of transmission and error checking.
The top layers examine the exchange of data between application programs. They
include protocols that specify file transfer, passwords and network management.
Handshaking
Data can only be successfully transferred between devices if handshaking occurs.
Handshaking is an agreement about which protocol to use to accomplish the
exchange of information. It is a series of signals that flow between devices during
data transmission. When using a modem, a handshake is those crunching sounds
heard when making a connection. Handshaking is needed between devices as they
may have different capabilities and may transfer data in different ways.
Handshaking involves sending signals to indicate the type of protocol to be
used. The transmitting device will send a signal and wait for an appropriate
response. When two devices successfully handshake, then a connection is made.
When a handshake is not successful, then the devices ‘hang up’ and try again.
There are two methods of handshaking to control the flow of data:
• Hardware flow control uses a dedicated connection, such as a wire. It is only
practical when devices are close enough to be linked with a cable. A common
hardware protocol is RTS/CTS (request to send/clear to send).
• Software flow control uses a special code sent with the data. It is used for long
distance communication. A common software protocol is XON/XOFF (X
stands for transmit). If a break in transmission is needed, then the XOFF
command is sent. When transmission is to start again, then the XON command
is sent.
Speed of transmission
The speed of data transmission is
determined by the transmitting
device and the bandwidth. The
bandwidth is the capacity of the
channel, or transmission medium. A
transmission medium with a high
bandwidth can transfer more data.
For example, a fibre-optic cable has a
high bandwidth. When cable
television is transmitted through
fibre-optic cable, many different
channels can be transmitted at the
same time.
Figure 3.2 Modem speeds are measured in bits
per second.
77
The speed of data transfer is measured by the number of bits per second or by
the baud rate:
• Bits per second (bps) is the maximum number of bits that can be transmitted
in one second. This measure of speed includes special bits used in asynchronous
transmission and any error checking bits. Bps is also called the bit rate.
• Baud rate is the maximum number of data symbols or electrical signals that
can be transmitted in one second. Because a data symbol can contain more
than one bit of data, the baud rate and the bit rate may be different. For
example, 1200 baud might transmit at 4800 bps.
Error checking
When data arrives at its destination, it may contain errors. These errors may
be caused by interference with the signal or simply by errors in encoding and
decoding the data. Errors must first be detected and then corrected. Three
common methods for error detection are parity checking, checksum and cyclic
redundancy check:
• Parity checking is a method of checking for errors in data transmission using an
additional bit called a parity bit. This bit is used only for the purpose of
identifying whether the bits being moved have arrived successfully. When data
is represented using an 8-bit ASCII, then a ninth bit is used that holds a 0 or a
1. When an odd parity is chosen, the number of ones in the nine bits must be
odd. This means that if the number of ones in the first eight bits is even, then
the parity bit must be one to make it odd. If the number of ones in the first
eight bits is odd, the parity bit must be zero to keep it odd. The sender and
receiver can also decide to send an even parity, in which case the number of
ones in the nine bits must be even. If an error has occurred in a single bit, then
the parity will be different and an error in transmission has occurred.
• Checksum is a method of checking for errors in data transmission by counting
the number of bits in a data packet. A data packet is created by dividing the
total data into smaller groups. The count of the bits in a data packet is attached
to the data packet. It is used by the receiver to check whether all the bits have
arrived successfully. If the count matches, it is assumed that a complete
transmission was received.
• Cyclic redundancy check (CRC) is a method of checking for errors in data
transmission using a division process. The data is divided into predetermined
lengths and divided by a fixed divisor. The remainder of the calculation is
attached and sent with the data. When the data is received, the remainder is
recalculated. If the remainders do not match, an error in transmission has
occurred. There are a number of different standards for CRC. A 32-bit CRC
achieves a 99.99% detection of all possible errors.
The most common form of error correction is to retransmit the data.
ITITFact
Fact
A Web gardener is a person who acts like an editor to ensure that
information posted on a Web page is accurate and relevant.
78
Core
Communication settings
The characteristics of the communication system are the basis of the communication settings. Communication settings can be changed by the user to
ensure a connection between two devices. The settings are often a parameter. A
parameter is a variable that is given a constant value for a particular application.
Some common parameters include bps, data bits, parity, stop/start bits and flow
control.
• Bits per second is the speed of transmission, such as 56 000.
• Data bits are the number of bits in each group of data. Each data group is
usually sent as a byte, such as 7-bit ASCII or an 8-bit ASCII.
• Parity is whether the data contains a parity bit for error detection. Parity is odd,
even or none.
• Stop/start bits are the number of stop and start bits used in asynchronous
transmission. This parameter is used to identify each byte. The normal range is
between 0 and 2. Some systems only use a stop bit.
• Flow control is the software handshaking protocol, such as XON/XOFF.
Figure 3.3 Parameters for a modem.
79
Exercise 3.1
1
2
3
4
5
6
7
8
9
10
Describe the five basic components of all communication systems.
Explain the difference between a protocol and handshaking.
What is the OSI reference model?
What is involved in the handshaking of two devices?
Describe software flow control as a method of handshaking.
What is the bandwidth?
Explain the difference between baud rate and bps.
Describe parity checking as a method of detecting errors in data transmission.
What is a cyclic redundancy check?
List five common parameters used to connect two devices.
LEARNING ACTIVITIES
1 All communication systems have five basic components. Identify the five
components in these systems:
a William writes a letter to a friend. He puts the letter into an envelope and sends
it through the mail system.
b Julia needs to transfer the directions of a conference venue to her partner. She
draws a diagram on a piece of paper and sends it using a fax machine.
2 The 7-bit ASCII character 1011011 is to be sent with a parity bit. What is the value
of the parity bit if the parity is even? The character was received with the ASCII
character of 1010001. Do you think the parity method of error detection would
have found the error in transmission? Why?
3 Cyclic redundancy checking is an error checking method used when transferring
files. Explain how CRC works. Describe another method of error checking. What is
one advantage of CRC over this other method?
4 A network is capable of transmitting data at 28 800 bps. How long would it take
to transmit a 400-Mb file? Characters are transmitted in 8-bit ASCII, including a
parity bit and an additional start and stop bit. What is the maximum transmission
rate over the network expressed in characters per second?
5 A high school and a primary school are trying to establish a communication link.
However, the link is not working. Describe any communication settings that need
to be investigated to ensure correct operation. Confidential student information
is to be sent using this link. Describe any methods of securing the data during
transmission.
6 Establish a communication link and transfer data between two computers.
Describe the steps taken to establish the link.
3.2 Examples of communication
systems
New communication capabilities have made it possible for people to do many
things that were not possible a few years ago. This section examines three
examples of communication systems: teleconferencing, messaging systems and
electronic commerce.
80
Core
Teleconferencing
Teleconferencing is the use of an electronic transmission to allow a meeting to occur
at the same time in different locations. It is an alternative to a face-to-face meeting.
Teleconferencing refers to communication, such as an audio conference or a video
conference, that goes beyond the normal telephone call between two people.
• An audio conference is a single telephone call involving three or more people
at different locations. It is a service provided by a telephone company. Audio
data is transmitted and received using the existing telephone lines.
• A video conference is a meeting that allows people in different locations to see
video images of each other on a screen, as well as hear speech. The least
expensive form of video conferencing is a tiny camera and a 4-inch window
displayed on a computer screen. In a typical business video conference, people
appear on a larger screen (see Figure 3.4). This may require special
communication arrangements because of the high bandwidth required to
transmit video.
Teleconferencing simulates a
face-to-face meeting and reduces
costs. Money is saved by not
buying airfares, hotel rooms and
meals. Teleconferencing also saves
people the time and energy
involved in travelling to attend a
face-to-face meeting. Teleconferencing is frequently used in
business and distance education.
However, tele-conferencing does
remove the inter-personal relationship achieved through a
face-to-face meeting. Physical
contact and informal discussions
are often needed to clarify ideas
and develop partnerships.
Figure 3.4 Video conferencing.
Messaging systems
A messaging system is used to send messages to people in different locations who
may receive the message at a later time. It has been used for centuries in the form
of letters. Messaging systems involve the creation, storage, exchange and
management of messages. Messages are sent to an individual or a group of people.
Traditional systems
Traditional messaging systems include the telephone and fax. They are communication systems used regularly by individuals and organisations.
• A telephone is a system for transmitting sounds or speech between distant
locations along telephone lines. It is a convenient method of communicating
with people around the world. A telephone answering system is a messaging
system. It stores messages and allows a person to hear the message at a later
time.
• A fax, or facsimile, machine is a system of transmitting and reproducing
documents by means of signals sent over telephone lines. The fax machine
81
scans a document and converts it into a bit-mapped image. This image is
compressed and transmitted along the telephone network to a destination fax
machine. This machine decompresses the image and reconstructs the original
document. Fax machines have become very popular as people can quickly
transfer a hard copy of a document or send a written message. Personal
computers equipped with a fax modem are capable of performing almost all
the tasks of a fax machine.
Voice mail
Voice mail, or v-mail, allows communication with other people by storing and
forwarding spoken messages. The sender dials a voice-mail number and records a
message. The message is digitally stored on a computer system and can only be
retrieved by the intended receiver of the message. To retrieve a message, you dial
into the voice-mail system using any telephone and enter an account number and
password. After you enter the voice-mail system, you can listen to the message,
delete it, save it or send it to another person.
Voice mail combines the features of a telephone answering system and some of
the concepts of email. It provides some advantages over email. More people have
access to a telephone than to a computer equipped for email. People also often
express their feelings more clearly with the spoken word. However, email is much
better at communicating complex information and sending different data types.
Electronic mail
Electronic mail, or email, allows communication with other email users by sending
and receiving electronic messages using a computer. Email was one of the earliest
uses of the Internet and is now widely used. It is fast, economical and a convenient
way to send messages to people all over the world. An email message can travel
around the world in minutes. To use email, you need a computer that is linked to
a network or the Internet, an account with an Internet service provider (ISP), an
email address and email software.
ITITFact
Fact
The Internet revolutionised email by turning countless incompatible networks into one global system. It is regarded as the messaging system for
the planet. Trillions of email messages are sent each year over the Internet.
Email can be written to anyone who has an email address. Email addresses are
unique and are obtained free. An email address consists of two parts separated by
the @ (‘at’) symbol in the form ‘name’@‘domain name’. The first part is the name
of the account. It is often a person’s username and is chosen when a user signs up
with an ISP. If a name is already in use by someone else at the domain, the user
may have to modify his or her preferred name by adding some more letters or
numbers. The second part is the domain name. It is the location of the person’s
account on the Internet. The domain name identifies the specific computer or
server where the person’s email messages are stored. For example, in the address
nick@ozemail.com.au:
• ‘nick’ is the name.
• ‘ozemail.com.au’ is the domain name. ‘Ozemail’ is the ISP, ‘com’ means the
domain is commercial, and ‘au’ is Australia.
82
Core
Most email messages contain two main parts: the header and the body of the
message. The header is similar to an envelope used in traditional letters. It contains
information needed to deliver the message. The sender’s email address is usually
automatically inserted, just like an envelope with a pre-printed return address. The
header contains four main parts that the sender fills in as required (see Figure 3.5):
• Email address (To:) is the address of the person receiving the message. It must
be correctly typed.
• Carbon copy (Cc:) sends the same message to other people apart from the
main recipient (optional).
• Blind carbon copy (Bcc:) sends a copy to other people without revealing that
these other people got the message (optional).
• Subject is the topic of the message or a brief description. This is very useful for
the receiver of the message (optional).
Figure 3.5 An email message.
The body of the message is typed using the email software or is imported or
copied from a word processor. Email messages are often short and typed very
quickly. Some people use inventive spelling in emails, such as coughy, bizzy, thanx
and enuff. The user does not have to be online to compose an email message.
Messages can be written offline and sent when the user logs onto a LAN or the
Internet. This saves money if the ISP charges by the hour for connection time.
When email is sent, it is stored on the server where the recipient has an account.
It stays on the server until the person checks his or her email.
After the email is read, it can be deleted, printed or stored in an appropriate
folder for later reference. The user can reply to an email message simply by
clicking on the ‘reply’ icon (see Figure 3.6). The address of the receiver (the sender
of the message being replied to) and the subject are automatically inserted in the
header of the reply. Leaving the subject the same identifies the ‘thread’ of the
message. The previous message can be retained so that the original sender
remembers the message. This is called quoting. Forwarding messages involves
sending messages you received to someone else.
83
Subject thread
Emoticon
Portion of
original message
‘quoted’
Figure 3.6 A reply to an email message.
Email software provides a number of features to help users create their email.
An address book is used to store email addresses (see Figure 3.7). This saves time
typing the address and avoids the problem of remembering each address. A
mailing list is a group of people who may want to receive the same messages. It
may be people working on the same project or a group of people with the same
interests. Mailing lists are created by entering the email address of each person in
the list and giving the list a name. A signature is several lines automatically
appended to outgoing email messages. It may include an email address, Web site,
graphic, occupation or telephone number.
Figure 3.7 An email address book.
84
Core
Electronic commerce
Electronic commerce, or e-commerce, is the buying and selling of goods and
services via the Internet. It has become a multibillion-dollar source of revenue for
the world’s businesses. E-commerce provides 24-hour availability, global reach,
the ability to interact and provide customer information, and a multimedia
environment. The most popular e-commerce sites sell computer products,
books, gardening products, music or office supplies (see Figure 3.8). However,
e-commerce is expected to expand into most retail areas. Each day, there are new
businesses being established that are based entirely on Web sales.
Figure 3.8 Amazon.com is a popular e-commerce site.
EFTPOS
EFTPOS (electronic funds transfer at point-of-sale) is a system that allows people
to purchase goods and services using a credit or debit card. It is the electronic
transfer of money from the customer’s bank account to the retailer’s bank
account. EFTPOS has made shopping easier for customers and allowed retailers to
immediately receive payment for their goods. Each point-of-sale terminal is linked
to the computer of the customer’s bank using the account number on the card.
Entering the PIN number is a security measure to identify the customer. When a
connection is made and approved, the money is immediately transferred.
Electronic banking
Electronic banking allows customers to view their account balances and
transaction histories, transfer money between accounts and pay bills using Bpay
(see Figure 3.9). It provides banking services 24 hours a day but cannot cater for
cash or cheque withdrawals. However, automatic electronic debits are becoming
more popular with consumers. Cheques are an expensive and inefficient way of
settling debts because the cheque passes through many hands before the
transaction is completed.
85
Figure 3.9 Internet banking services.
Some electronic banking providers require customers to download special
banking software and install it on their personal computer. Electronic banking
raises the issue of security. All banks are determined to make their online banking
services safe from inference and to secure customer details. Data encryption is
used to secure the data transfer between the customer’s computer and the bank’s
computer.
Exercise 3.2
1
2
3
4
5
6
7
8
9
10
What is teleconferencing?
Outline the advantages and disadvantages in teleconferencing.
What is a messaging system?
How does voice mail work?
Describe the two parts of an email address.
List the four main parts in the header of an email message.
Why are email messages sometimes written offline?
What is a mailing list?
Describe some the benefits of e-commerce.
What is provided by electronic banking?
LEARNING ACTIVITIES
1 Communication systems perform information processes requiring participants,
data/information and information technology. Clearly identify the participants,
data/information, information technology and the purpose of the following
communication systems:
86
Core
2
3
4
5
6
a teleconferencing
b messaging systems
c electronic commerce.
Construct a chart to compare the advantages and disadvantages of three
messaging systems: a traditional system, voice mail and electronic mail.
Create a brief email message about this Information Processes and Technology
course.
a Send the email message to a partner and a carbon copy to the teacher.
b Check that your partner received the email message.
c Send a reply to your partner by quoting.
d Forward your original message to another person in your class.
Create an email questionnaire on communication systems.
a Design a simple questionnaire with only one or two questions.
b Create a mailing list and send the email questionnaire to the mailing list.
c Store the replies in a separate folder. Collate the results. A spreadsheet is a
useful tool to collate and graph the results.
d Distribute the results of the survey to the people on the mailing list and thank
them for their participation.
David frequently uses the Internet to access information. Briefly outline the issue
of copyright in relation to the Internet.
Kerry recently downloaded banking software for electronic banking. Describe
the process of downloading. Describe two factors that affect the speed of
transmission.
3.3 Transmitting and receiving
Transmitting and receiving refers to the transfer of data and information. It is
carried out using numerous communication concepts and completed by network
hardware and software.
Communication concepts
Communication concepts include the transmission of data, protocols, handshaking, networks, network topologies and network access methods.
Transmission of data
Data is transferred between devices in two ways: serial transmission and parallel
transmission. Parallel transmission is the transmission of data simultaneously using
separate channels. Serial transmission is the transmission of data one after the
other. Serial transmission is used to transmit data to peripheral devices, such as
modems and printers, and is used on networks.
Serial transmission can be either synchronous or asynchronous. Asynchronous
transmission is the sending of data by identifying each byte with special start and
stop bits. It has become the standard for personal computers. Part of protocol
agreement is to specify how many start and stop bits. The normal range is between
0 and 2. Synchronous transmission requires all the data to be sent at the same
rate. The same number of bytes is sent each second. This is synchronised by each
device using a clock. Synchronous transmission is faster and more efficient than
asynchronous transmission as there are no extra bits. It is used on larger computer
systems. (See Figure 3.10.)
87
Character 6
Character 7
Source
Character 4
Character 5
Character 3
0 1 0 1 0 0 1 1 1 1 0 1 1 0 0 0 1 1 1 0 0 1 1 0 0 1 1 0 1 1 0 1
Receiver
Synchronous transmission
Source
1 0 0
Start
bit
Character 6
Character 5
1 0 1 1 1 1 0 1 1 0
1 0 0 0 1 1 1 0 0 0
Stop
bit
Start
bit
Stop
bit
Start
bit
1 0 1
Receiver
Stop
bit
Asynchronous transmission
Figure 3.10 Serial transmission.
The direction of data flow can be simplex, half-duplex or full-duplex mode.
Simplex mode allows transmission in one direction only, from the sender to the
receiver. An example of simplex mode is the radio, a telegram or television. Halfduplex mode allows transmission in both directions but not at the same time. This
means the sender and the receiver take turns. An example of half-duplex mode is
an intercom, walkie-talkie or disk drive. Full-duplex mode allows transmission in
both directions at the same time. Most communications systems, such as the
telephone or email, use full-duplex mode.
Protocols and handshaking
A protocol is a set of rules that governs the transfer of data between computers.
Protocols define how a link is established, how data is transmitted and how errors
are detected and corrected. When the same protocols are used, different types of
computers and other devices can communicate with each other. Numerous
protocols have been developed for specific technologies (see Table 3.1). Protocols
change over time and often are the basis for the development of a particular
product.
When an agreement is reached about which protocol to use, it results in an
exchange of information. Handshaking involves sending signals to indicate the
type of protocol to be used for an agreement to be reached. Handshaking is
needed as modems at each end of the line may have different capabilities. For
example, they need to inform each other about and agree on the highest
transmission speed.
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Core
Protocol
Description
IPX
Internet Packet Exchange. A NetWare data delivery protocol used by
Novell’s NetWare Operating System.
SNA
Systems Network Architecture. A protocol that defines data
communication on a network. It was originally used to link mainframes.
FDDI
Fibre Distributed Data Interface. A protocol that specifies computer
input/output interface standards using fibre-optic cables.
X.25
The standard packet switching protocol. It is used for low-speed
applications, such as credit card verifications and automatic teller
machine transactions.
ATM
Asynchronous Transfer Mode. A standard transport protocol that
specifies a method of packaging data into cells. It transmits all data
types over any type of media.
Kermit
Asynchronous communication protocol for transmission of files using
the public telephone network.
XModem
File transfer protocol developed in the late 1970s for personal
computers. Data is transferred in blocks 128 bytes long. XModem
originally supported checksum but later versions support CRC.
YModem
File transfer protocol developed as an extension to Xmodem. Data is
transferred in blocks 1024 bytes long. YModem includes such features
as transfer of filenames, increased reliability of error checking and
increased data transfer.
ZModem
File transfer protocol developed to rectify the limitations associated
with YModem. ZModem uses a variable block size and supports CRC. It
provides for high-speed packet and network communication
environments.
TCP/IP
Transmission Control Protocol/Internet Protocol. A common set of rules
for data transmission and error detection across the Internet. It works
by breaking information into smaller packets of data.
HTTP
Hypertext Transfer Protocol. A protocol that enables the user to send
and retrieve files using the Internet. HTTP allows access to Web pages
that are based on hypertext.
FTP
File Transfer Protocol. A protocol used to enable the client computer
(user) to log on to the server. FTP is the oldest form of remote file
access for the Internet.
POP
Post Office Protocol. A protocol that specifies how email messages may
be exchanged between a computer and the ISP.
MIME
Multipurpose Internet Mail. A protocol designed to enable files to be
sent across the Internet as email.
Table 3.1 Common data transfer protocols.
Networks
A network is a number of computers and their peripheral devices connected
together in some way. Each device in a network is called a node. The nodes in a
network include many different types of devices, such as printers, storage devices,
terminals and workstations. Terminals are devices that send data to and receive
data from another computer system. If the terminal has both memory and
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processing capabilities, it is called an intelligent terminal. Most personal
computers are classified as intelligent terminals and are called workstations on a
network.
The simplest form of a network is when one computer is connected directly to
another computer, using a cable. However, a network can also consist of thousands
of computers connected together. Networks are classified as local area networks or
wide area networks:
• Local area networks (LANs) connect computers within a building or group of
buildings on one site. LANs cover a small geographical area, and the computers
are linked together by coaxial cable or fibre-optic cable. There are three main
advantages in using a LAN:
– sharing limited hardware resources, such as printers, hard disks and modems
– sharing application software, such as word processing, database, spreadsheet
and graphics programs
– improved communication among users by sending electronic messages.
• Wide area networks (WANs) connect computers over hundreds or thousands
of kilometres. WANs often consist of a mainframe computer called the host
and a number of terminals. For example, the EFTPOS terminals of many retail
organisations and the ATM terminals of banks are all part of a WAN (see Figure
3.11). A WAN may use a private leased line, the normal telephone network or
a combination of both. A private leased line is dedicated to the network. It
offers higher transmission speeds and more accurate transfer of data than those
available through the public switched telephone network (PSTN). PSTN links
are relatively cheap if computers do not require constant connection. However,
PSTN links are not guaranteed and can be interrupted.
Most data sent over a network
uses packet switching. Packet
switching is a technique that
divides messages into small data
packets, transmits the packets and
later joins the packets to form the
original message. It allows multiple
users to use the same transmission
line by interspersing the data
packets from different users. Data
packets may not be sent along the
same path and could arrive at
the destination at different times
and in the wrong order. Each data
packet contains an address and
control instruction to reassemble
the message in the correct order.
Data transfer on the Internet is
based on packet switching.
Figure 3.11 EFTPOS uses a WAN.
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Core
ITITFact
Fact
The word ‘packet’ was coined by people working on ARPANET to divide
long messages generated by their computers. The ARPANET was a network
developed in 1969 by the U.S. Department of Defense that later expanded to
become the Internet.
Network topologies
Network topology is the physical arrangement of the devices in a network. There
are many possible network topologies, such as star, bus and ring (see Figure 3.12).
Bus Network
Star Network
Ring Network
Figure 3.12 Common network topologies.
A star topology has a central computer with each device connected directly to
it. The central computer serves as a switch. It receives messages and sends them to
the destination device. Star topology requires extra cabling because each device
needs a cable to the central computer rather than to the nearest device. If one
device or cable is broken, the network can still operate. However, if the central
computer fails, then the network fails. It is also limited by the processing power of
the central computer. Star networks use a time-sharing system that allocates a
certain amount of CPU time for each user. It is the most common topology for
a mainframe.
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A bus topology is an arrangement where all the devices are attached to a direct
line called the bus. Each device has a unique identity and can only recognise those
signals intended for it. Devices check the bus and retrieve their messages as data
travels along the bus. Each device is considered to be connected to every other
device and can communicate directly along the network to any other device. Bus
topology is one of the easiest to set up and can still operate if one node fails.
Ethernet and PowerTalk use a bus topology.
A ring topology is an arrangement where all devices are attached so that the
path is in the shape of a continuous circle. Each device in the ring has a unique
address. Data flow is in one direction, moving from device to device until the data
arrives at its destination. The token ring network is the most common form of
access for ring topology.
Network access methods
There are a number of ways of dealing with multiple users wanting to access the
network at the same time. The two most common access methods are Ethernet
and token ring:
• Ethernet—the first industry-standard LAN access method, or protocol, based
on a bus topology. Ethernet allows data to be transmitted simultaneously to all
nodes on the network in both directions. Addressing information allows each
node to recognise and receive individual data packets intended for it.With data
packets travelling simultaneously, collisions will occur and will cause errors. To
overcome this problem, Ethernet uses a method called Carrier Sense Multiple
Access and Collision Detection (CSMA/CD). In CSMA/CD, all nodes have
the ability to sense signals on the network. When a node wishes to transmit, it
‘listens’ to the bus for signals. When there is no signals on the bus, it transmits.
However, occasionally a collision will occur if two nodes sense a clear bus at
the same. When a collision is detected, each device stops transmitting and
then retransmits at another time. Ethernet is defined in a standard called
IEEE 802.3.
• Token ring—a LAN access method, or protocol, based on a ring topology.
The token ring operates by continually passing special data packets called
tokens between nodes on the network. Workstations with data to send capture
a free token and attach data along with addressing information. A busy token
with data cannot be used by other nodes. When the data arrives at the
destination, the data is replaced with an acknowledgment and sent back to
original sending node.
ITITFact
Fact
A ‘phreak’ is a person who breaks into the telephone network illegally.
Pheaks typically try to make free long-distance phone calls or to tap phone
lines. However, the term is sometimes used to include anyone who breaks or
tries to break the security of any network.
Network hardware
Networks are not just made up of cables connected to such devices as computers,
terminals and printers. Several special-purpose hardware devices are needed to
successfully construct a network.
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Network interface card
Each computer connected to the network requires a special network interface
card. A network interface card (NIC, pronounced ‘nick’) is an expansion card that
fits into an expansion slot of a computer or other device, so that the device can be
connected to a network. Most NICs require a network cable connection and have
connectors on the card for different types of cables. The type of NIC depends
upon the type of network. NICs package data according to the rules of the
network operating system and transmit data along the connecting network cable.
Servers
A server is a computer that provides services to other computers on the network.
Individual computers log on to the server, which gives them access to files,
applications or peripheral devices. There are different types of servers, such as file
servers, print servers, mail servers and Web servers.
• A file server is a controlling computer in a network that stores the programs
and data shared by users. The files stored on this server can be retrieved by any
node provided it has access rights.
• A print server is a computer in a network that controls one or more printers
and stores data to be printed. A print server can be used with or without a file
server.
• A mail server is a computer in a network that provides email facilities. It stores
incoming mail for distribution to users and forwards outgoing mail to
appropriate devices.
• A Web server is a computer in a network that provides a connection to the
Internet. All the Internet traffic is directed through this server.
Routers and switches
Data often travels between networks. This requires networks to be linked to other
networks, paths to be established between the networks and signal strength to be
boosted.
Devices used to determine the path between networks include:
• Router—a device that determines where to send a data packet between at least
two networks. Its decision is based on its current understanding of the
networks. A router maintains a table of the available routes and their
conditions. It uses this table together with distance and cost algorithms to
determine the best route for a given data packet. Data packets often travel
through a number of networks and routers before arriving at their destination.
• Switch—a device that directs data packets along a path. It may include the
function of a router. In general, a switch is a simpler and faster mechanism than
a router as it does not maintain knowledge of the networks. A switch is not
always required in a network. Many LANs are organised so that the nodes
inspect each data packet.
Bridges and gateways
The actual interconnection between networks is achieved using devices such as
bridges and gateways.
• Bridge—a combination of hardware and software to link two similar networks.
It often connects LANs that use the same protocol, such as Ethernet. A bridge
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examines each data packet on a LAN and forwards any data packets addressed
to a connected LAN. Bridges are faster than routers because they connect
networks that are using the same protocol.
• Gateway—a combination of hardware and software to link two different types
of networks. This usually involves converting different protocols. For example,
a gateway could be used to convert a TCP/IP packet to a NetWare IPX packet.
A signal may be corrupted due to long distances or interference from
electromagnetic fields. A repeater is used to rebuild a fading signal to its original
strength and shape before transmitting it onwards. It ensures that the data is
received as it was sent. A network repeater is used in a LAN to connect network
segments. Repeaters are less intelligent than a bridge or gateway.
Hubs
A hub is a central connecting device in a network. Data arrives at the hub from
one or more devices and is forwarded out using just one cable (see Figure 3.13).
For example, four cables from three computers and a printer are connected to a
hub and then a single cable connects the hub to a server. A hub can also include a
router. Most hubs were originally passive. The data simply passed through the hub
without any change. Intelligent hubs are more frequently used in today’s
networks. They often contain a CPU and network operating system. This allows
them to perform some of the functions of a server.
24 computers
Switch
gh
Hi
k
lin
ed
e
sp
Each computer
on a 10 Mb/sec lin
Switch
Computers sharing
10 Mb/sec line
Server
Hub
Hub
Hub
Figure 3.13 Network hardware.
Transmission media
Data is transferred along a transmission medium. The capacity of the transmission
medium is called the bandwidth, and it is measured in bits per second. A
transmission medium with a high bandwidth can transfer more data. Transmission
media are categorised as either wire transmission or wireless transmission.
Wire transmission transfers the data through wires and cables. These cables
must be protected from damage, they take up space, and they can be difficult to
install. However, wire transmission can carry large amounts of data with little
interference from other signals. Wire transmission media include twisted-pair,
coaxial or fibre-optic cable (see Figure 3.14).
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Core
• Twisted-pair cable consists of two thin insulated copper wires, twisted to form
a spiral. Twisting reduces the amount of interference from other cabling. The
two main types of twisted-pair cables are unshielded twisted-pair (UTP) and
shielded twisted-pair (STP). UTP is the most common. STP is used in ‘noisy’
environments where its shield protects against excessive electromagnetic
interference. Twisted pair is the slowest medium, with a bandwidth up to
60 Kbps.
• Coaxial cable (or coax, pronounced ‘co-axe’) consists of a single copper wire
surrounded by an insulator, grounded shielding and an outer insulator. The
shielding allows data to be transmitted with little distortion. It is commonly
used over distances of less than a few kilometres. The bandwidth for a coaxial
cable is 10 Mbps.
• Fibre-optic cable uses a laser of light to carry data in small glass fibres about
the diameter of a human hair. It is free from electromagnetic and radio
interference, is very secure and can transmit data at high speeds without errors.
Fibre-optic cables are replacing conventional copper-wire cables. The bandwidth for fibre-optic cables is in excess of 400 Mbps. A single strand of optical
fibre can carry thousands of telephone conversations.
Twisted pair
Fibre-optic cable
Coaxial cable
Conductor
Insulator
Covering
Outer insulation
Grounded
shielding
Cladding
Insulation
Glass
optical fibre
Inner conductor
Figure 3.14 Wire transmission.
Most LANs use either twisted-pair cable or coaxial cable. Fibre-optic cable is
usually too expensive and difficult to install.
There are two types of transmission used: baseband and broadband. Baseband
networks use the entire capacity of the cable to transmit only one signal at a time.
Most LANs are baseband. Broadband networks divide the cable so that several
signals can be transmitted at the same time.
Wireless transmission moves the data through air and space. It does not need
a fixed physical connection between the source and the destination. Radio and
television are examples of wireless transmission. Wireless transmission involves
microwaves, satellites, wireless networks and mobile phones.
• A microwave is a high-frequency radio signal sent through space in a straight
line from one antenna to another. Microwaves have been used for several
decades to transmit both voice and data. Antennas are placed on tall buildings
or mountain tops to continue transmission over long distances (see Figure
3.15). Microwave transmission is faster than telephone lines or coaxial cables.
Even though it is reasonably error free, weather conditions or such objects as
trees and buildings can obstruct the signal and affect the transmission.
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Antenna
50 km
Antenna
Signal
Figure 3.15 Microwave transmission.
• A satellite is a specialised receiver and transmitter that is launched by a rocket
and placed in orbit around the earth. A signal is sent from one ground station
to the satellite, which receives and retransmits the signal to another ground
station. Each ground station uses a satellite dish to send and receive the signals
(see Figure 3.16). Satellites can transmit large amounts of data over long
distances and at great speeds. There are hundreds of satellites currently in
operation. They are used for weather forecasting, television broadcasts, radio
communications and Internet communications.
• Wireless LANs use radio waves, not
cables, as their transmission medium.
Problems in maintaining signal quality and
concerns about electromagnetic radiation
have not made wireless networks popular.
• Mobile phones transmit data to a grid of
cellular stations that are linked to the wiretransmission telephone network. Mobile
phones use radio waves to communicate
with the cellular station. They are portable
devices, and monthly service fees and percall costs are higher than those for a normal
telephone in most countries.
Figure 3.16 A satellite dish.
Network software
Each computer in a network must have appropriate network software. This
software contains the ‘rules’ for communication and determines how the network
devices send and receive data. Network software is organised by a network
administrator. A network administrator is a person who manages a network within
an organisation. His or her responsibilities include network security, installing new
applications, distributing software upgrades, monitoring daily activity, enforcing
licensing agreements, developing a storage system and providing routine backups.
These responsibilities are completed using the network operating system.
Network operating systems
A network operating system (NOS) is an operating system that is designed
primarily to support computers connected on a LAN. Some common examples of
network operating systems are Novell’s Netware, Artisoft’s LANtastic and
Microsoft’s Windows NT (see Figure 3.17). One part of the network operating
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Core
system resides in each node and another resides in the server. The network
operating system performs a range of different tasks.
Figure 3.17 Windows NT Web site.
Network operating system tasks
The network operating system controls the flow of data between the devices on
the network and controls the requests for data. It organises messages from nodes
until the network is ready to process each message. The tasks performed by a
network operating system include:
• administration—adds, removes and organises users; installs hardware devices
and software applications; and carries out maintenance operations, such as
backup
• file management—gives users access to the remote hard disks on the server and
provides a file system and the ability to manage a network directory
• applications—handles requests from users to share data and applications
• resource management—allows network devices, such as printers and modems,
to be shared; assigns users to printers; and orders print jobs
• security—monitors and restricts access to network resources.
Logon and logoff procedures
When a user connects to a network, the user is granted a certain level of access.
This is done during the process of logging on. Logon is the procedure used to get
access to the network. The user is identified by means of a user ID and a password.
The user ID usually conforms to a limited length, such as eight characters; and the
password often must contain at least one digit. The password is an important
security measure and must be not be readily available or an easily guessed word,
such as a nickname. The network must also keep passwords secure. The password
file should be encrypted and protected from unauthorised access. Network systems
may require users to frequently change their passwords as a security measure.
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The logon procedure usually allows the user two or three attempts to enter the
correct name and password. Mistakes can occur in typing or in the communication
link. After logging on, the user is given access to only those features authorised by
the network administrator.
The correct procedure for logging off should always be carried out. It clears the
communication line for another user.
Intranets
An intranet is a private network that uses a similar interface to the Web. It usually
has a connection to the Internet and consists of many interlinked LANs. The main
purpose of an intranet is to share information and computing resources among the
employees of an organisation. The information may be staff news, product
information, telephone directories, policies, employee manuals or calendars. When
the intranet provides access to the Internet, it is through firewalls. Firewalls
monitor the flow of data in both directions to maintain the security of the
organisation.
An extranet is an intranet that is accessible to customers, suppliers or others
outside the organisation. It provides such information as product descriptions,
answers to frequently asked questions, warranties and how to contact customer
service. Organisations are attempting to make extranets easy to use and a source
of relevant information.
ITITFact
Fact
Infosurfing is using the Internet to get the maximum information in the
shortest amount of time. It favours textual content over images. Infosurfing
is practiced by people who become impatient waiting for multimedia to load
or who just need to focus on text.
Exercise 3.3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
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Core
Explain the difference between simplex, half-duplex and full-duplex mode.
Describe the function of a protocol.
Explain the difference between the YModem and the ZModem protocols.
Describe an X.25 protocol.
What is the difference between a LAN and a WAN?
Describe the advantages of using a private leased line.
What is packet switching?
Explain the difference between a bus topology and a ring topology.
Describe the way a LAN transmits messages using an Ethernet and using a token
ring.
Describe the collision-detection mechanism used on an Ethernet.
Describe four different types of servers.
How does a router determine where to send a data packet?
Explain the difference between a bridge and a gateway.
What is a hub?
15
16
17
18
19
20
21
Describe three methods of wire transmission.
Explain the difference between baseband and broadband.
Describe microwave as a transmission medium.
What are the responsibilities of the network administrator?
Describe the tasks performed by a network operating system.
Describe the process of logging on to a network.
What is the main purpose of the Intranet?
LEARNING ACTIVITIES
1 Gloria connected to a remote computer. She used the following communication
settings: 7-bit ASCII, 1 start bit, 1 stop bit, odd parity, and 4800 baud. What is this
type of transmission? Explain the type of error detection method used in this
connection. What is one major deficiency of this method? Describe an alternative
error detection method that would provide better results.
2 A LAN is to be constructed with seven nodes, using a ring topology. Draw a
diagram to show this arrangement. How will this network transfer data? Describe
how the network will overcome the problem of multiple users.
3 The management of a large organisation has decided to connect two LANs. What
are some of the benefits to the organisation if the LANs are linked? One LAN uses
the Ethernet protocol and the other a token ring protocol. Name a device that
could be used to connect the LANs. What does this device do?
4 An organisation is planning to introduce two LANs, one in each of two different
buildings on the same site. These networks are to be linked together. The
organisation decides to install a bus network for both LANs. Draw a diagram to
show this arrangement. How will each LAN transfer data? Describe how the
network will overcome the problem of multiple users. Describe a device that could
be used to connect the two LANs.
5 A large organisation uses a LAN that has a bus network topology. The network has
a file server, one print server, a printer and six workstations. Draw a sketch of this
network. Describe the function of the print server. A mail server is to be added to
the network. What is the function of a mail server? Describe any procedures that
could be used to provide security for files on the network.
6 Investigate a LAN either at your school or in the local community. Draw the
topology of the LAN. Describe the advantages of this network topology over other
topologies. List the types of problems likely to be encountered on this type of
network. What network software controls the functions of this LAN? List the tasks
performed by the network software.
7 Explain the differences between an intranet and the Internet for transmitting and
receiving information in a communication system. What do these communication
systems have in common?
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All information processes play a role in communication systems, including
collecting, processing and displaying.
Collecting
Collecting data for a communication system involves generating the data to be
transmitted. For example, a person using an ATM generates data by inserting a
transaction card and typing a request on a keyboard. This data is collected and
transmitted to the bank’s computer. Another example is when a salesperson in a
shop scans the barcodes of a product. The product’s details are collected and
transmitted to a central computer.
Collecting data involves a range of collection devices to gather different types
of data. The choice of device depends on the application and the type of data to
be transmitted. Some collection devices include:
• ATM terminals for electronic banking
• EFTPOS terminals for a retail store
• telephones for voice mail
• keyboards for electronic mail
• video cameras for a surveillance system.
ITITFact
Fact
Internesia is an inability to remember on which Web site an item of
information was located. People suffering from internesia often bookmark
so many sites that they cannot find anything by using their bookmark list.
Processing
In a communication system, processing data is the manipulation of the data. After
the data is collected, it must be converted into a form for transmission. This
process involves encoding and decoding.
Encoding and decoding
Encoding involves converting data from its original form into another form for
transmission. Decoding is the reverse process. It converts data from the form used
for transmission back into the original form. For example, a telephone encodes the
sounds from your voice into electrical pulses that can be transmitted along the
telephone lines. The telephone receiving the call decodes the electrical pulses back
to the sounds of your voice. The type of encoding and decoding depends on
whether the original data is in analog or digital form.
Analog data is represented by using continuous variable physical quantities,
such as voltages. For example, a clock that displays the time by hands moving
smoothly around the clock face is an analog device. At any moment, the clock will
give you an instant measure of the exact time, since you can estimate parts of a
second as the second hand moves. Most natural events in the real world, such as
temperature, light and pressure, are in analog form. They change smoothly and
slowly like the hands of the clock. Sounds, images and video are naturally in analog
form. Analog signals are pulses, usually electrical or optical, in the form of a
continuous wave.
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Digital data is represented in the form of digits or numbers. For example, a
digital clock shows the time as a certain number of hours and minutes. The time
changes in a series of jumps. Numbers, text and other characters are naturally in
digital form. Information technology works with data in a digital form. Digital
signals are represented as a series of 0s and 1s.
The form of the data (either analog or digital) and the transmission signal
(either analog or digital signal) affects the quality of the data received and the cost
of transmission. The quality of analog data depends on maintaining the exact wave
as it moves through a wire or space. If it is corrupted in any way, there is no way
of regenerating the wave. However, digital data is transmitted as a series of 0s and
1s, and it is possible to regenerate data that has been corrupted. That is, to
reconstruct the data, it is only necessary to distinguish between a 0 and a 1.
As discussed previously, common methods for error detection include parity
checking, checksum and cyclic redundancy check.
There are four encoding and decoding possibilities in transmission:
• Analog data to analog signal. The wave shape of the data is encoded into the
signal. A telephone encodes analog data in the form of sounds into analog
signals suitable for the telephone line. If the signal is corrupted, there is no way
of restoring the original analog data.
• Digital data to analog signal. A series of 0s and 1s is encoded into a continuous
wave. A modem encodes (or modulates) digital data from a computer into
analog signals for the telephone line. When the analog signal is received by
another modem, it decodes (or demodulates) the analog signal into digital data
(see Figure 3.18).
• Digital data to digital signal. A series of 0s and 1s is transmitted by sending it
through a channel as a series of on and off pulses. Data transmitted in a LAN
is digital data using a digital signal. There is a low error rate for this type of
transmission. Digital data is encoded (changed) into a digital signal by the
computer or a specific peripheral device.
Computer
Digital signal
1
1
0
1
0
1
0
1
0
0
Modem
Analog signal
1
0
1
0
Phone line
Modem
1
1
0
1
1
1
0 0 0 0
Digital signal
Computer
Figure 3.18 A modem encodes digital data to analog signals and decodes analog signals to digital data.
101
• Analog data to digital signal—the wave shape of the data is encoded into a
series of 0s and 1s. This process of generating digits or numbers is called
digitising. Images are digitised using such devices as scanners, and sounds are
digitised using a process called sampling. The transmission of television using a
cable is an example of analog data to digital signal.
Attachments
Attachments are computer files, such as text, video, sound, pictures or programs,
sent with an email message. Clearly, the receiver of the email must have an
application that can read or convert the file. When sending attachments, it is
important to include a brief explanation in the main body of the email. The
explanation should state that there is an attachment and give its filename and
its format.
All email programs need to ‘encode’ file attachments into characters since the
Internet TCP/IP protocol does not allow transmission of binary code. Many email
programs use the Multipurpose Internet Mail Extension (MIME) protocol to do
this. It is an Internet protocol that is able to negotiate many different operating
systems and types of software. It has been a major step forward in the ability to
exchange files other than plain-text files.
Client-server architecture
Client-server architecture describes the software relationship between the client
(user) and the server. A client sends a request to a server according to an agreed
protocol, and the server responds. It is
similar to a customer (client) sending
an order (request) on an order form
(protocol) to a supplier (server) for
particular goods (data). Client-server
architecture provides a convenient way
to interconnect programs that are
distributed across different locations of
a network. Most business applications
today use a client-server architecture, as
does the Internet. The Web browser is a
client program that requests services
from a Web server to complete the
request. Ideally, a server should provide
a user-friendly interface so that clients
are not aware of the information
technology that is providing the service.
Displaying
Displaying is the presentation of information in the form of text, numbers, images,
audio or video. A range of hardware and software combinations can be used to
display different types of information in a communication system such as a
telephone and an EFTPOS terminal:
102
Core
• Telephone. Audio information is displayed using a telephone. A telephone
contains a transmitter that converts sound into a signal suitable for the
transmission medium and a receiver that converts the signal back into sound.
When a message is retrieved from voice mail, the telephone is the display
device used to listen to the message.
• EFTPOS terminal. Information about EFTPOS transactions is displayed using
an EFTPOS terminal. The EFTPOS terminal contains a screen to display the
name and price of the product being purchased. When the customer’s bank has
been contacted, then the EFTPOS terminal displays the approval if funds are
available. The EFTPOS terminal provides a receipt for the customer of all
transactions.
ITITFact
Fact
Netscape sometimes uses a cartoon character called Mozilla as a mascot for
its products. Mozilla was Netscape’s original name for Navigator. It was
used by Navigator’s developers as a follow up to Mosaic.
Exercise 3.4
1
2
3
4
5
6
7
8
9
List five collection devices used in communication systems.
Explain the difference between encoding and decoding.
What types of data are naturally in analog form?
How are digital signals represented?
Describe the processing of digital data to an analog signal.
Describe the processing of analog data to a digital signal.
How does the client-server architecture work?
Describe the Internet as a client-server architecture.
What information is displayed by an EFTPOS terminal?
LEARNING ACTIVITIES
1 What is the difference between an analog and a digital signal? Draw a diagram to
illustrate your answer. Describe one device that converts analog and digital data.
2 Information resources sharing is usually provided by a file server or a client server
method. Illustrate the difference between these methods when a request is made
to an account file for all customers who have a balance of over $5000.
3 EFTPOS terminals are used to carry out some of the information processes in a
communication system. Examine EFTPOS terminals and classify the procedures in
terms of the information processes.
4 Create an email message that contains an attachment, such as a simple graphic.
The email is to contain a brief explanation of the attachment.
a Send the email message to a friend and a carbon copy to the teacher.
b Check that your friend received the email message and could open the
attachment.
103
3.5 Issues related to
communication systems
Both positive and negative impacts arise in the use of communication systems.
In this section, we examine some of the social and ethical issues raised by
communication systems.
Messaging systems
Messaging systems have improved communication between people; however, they
have raised a number of issues:
• Social context. Ideas delivered by messaging systems appear less forceful and
caring than ideas delivered personally. Messaging systems have difficulty when
communication depends on users expressing their feelings.
• Danger of misinterpretation. Communication often depends on the context,
inflection in the speaker’s voice, and body language. For example, ‘this has been
a great day’ could have a negative or a positive meaning depending on the way
the words are spoken. This phrase could easily be misinterpreted using email or
a fax. There are also dangers with voice mail and the telephone, as body
language is not communicated.
• Power relationships. Messaging systems may change the relationship between
people in an organisation. For example, email could provide an easy avenue for
the lowest paid worker of an organisation to provide information to the senior
manager. The normal method of communication through middle management
is affected.
• Privacy and confidentiality. A characteristic of messaging systems is that the
messages are stored. Email and voice mail store messages on servers, and these
can be accessed by the people who are providing the service. Hackers may also
break the security of these servers. Telephone conversations can be intercepted,
and fax messages can be read by anybody near the machine. Clearly, messaging
systems do not guarantee the privacy and confidentiality of messages.
• Electronic junk mail. Unwanted mail is a problem for messaging systems.
People can send an email message to one person or thousands of people
(spamming) very easily. It may simply be a message about a product or service.
However, if a person receives hundreds of junk emails each day, it takes up
valuable time. Prohibiting this practice would be difficult and compromise
our free society.
• Information overload. This term refers to the enormous amount of information
that people have to absorb. Messaging systems are a source of information. The
large amount of email and voice mail received by some people has increased
their workload and caused stress. There is often an expectation that people will
respond more quickly to email and voice mail than to a letter or to a telephone
message written down by someone else.
ITITFact
Fact
The volume of information that is absorbed in one week at the end of the
20th century is more than a person received in a lifetime at the beginning of
the 20th century.
104
Core
Internet
Many social and ethical issues have been raised by the use of the Internet. Some
of the issues include Internet trading, censorship and Internet banking.
Internet trading
Internet trading, or e-commerce, is increasing at a staggering rate to meet the
needs of consumers. Most experts predict that Internet trading and the number of
customers on the Net will continue to rise in the next few years. E-commerce is
presently valued at approximately $200 billion. Many businesses are establishing
a Web site to promote their goods and services. The Internet provides significant
advantages for consumers, such as more information about products and services,
shopping globally and increased competition that has resulted in lower prices.
Some of the implications of Internet trading include:
• Taxation. Present governments have been unable to tax transactions on the
Internet. The increased business on the Internet will reduce the money
governments receive from their goods and services taxes.
• Employment ramifications. The increase in Internet trading requires more
people to be employed in the information technology industry. It may result in
fewer shop fronts and fewer people employed to provide this type of service.
• Nature of business. Traditional businesses that provide opportunities for
human interaction are being challenged. For example, people are choosing to
buy their groceries using the Internet instead of visiting the store (see Figure
3.19). People can complete some of their business at home without the hassle
of travelling.
• Trade barriers. The developments in communication technology have made
trade barriers between countries irrelevant. The whole issue of where one
country ends and another one begins is open to question. People are buying
and selling goods on the Internet with little thought given to the countries
involved or to trade barriers.
Figure 3.19 Internet shopping.
105
Censorship
One of the most controversial issues to have arisen with the Internet is censorship.
The Internet provides access to a large amount of offensive material, such as
pornography, racism and violence, and the information is not hard to find. The
Internet allows children to access any material they wish, either deliberately or
unintentionally. Some people believe that offensive material should be banned,
while others argue that banning any material compromises our free society.
There have been many unsuccessful attempts to censor material on the Internet
by governments and law enforcement bodies all around the world. The Internet
Industry Association (IIA) represents Australian ISPs (see Figure 3.20). It has
released a code of conduct that deals with censorship of online content. The code
requires ISPs to remove offensive content from their servers and to block access to
classified material hosted on overseas sites. The federal government has passed a law
requiring ISPs to subscribe to the IIA’s code. The difficulty with enforcing censorship
is the enormous number of Web sites and the fact that thousands of new sites are
published daily. Monitoring Web sites on a global basis is impossible. Clearly multinational agreement is needed on offensive material. However, this agreement may
be difficult to obtain and regulate. The prime responsibility for preventing children
from accessing offensive material rests with parents and teachers.
Figure 3.20 The IIA’s Web site provides access to the IIA’s code of practice.
Internet banking
Internet banking allows customers to view their account balances and transaction
histories, transfer money between accounts, and pay bills using Bpay. It provides
banking services 24 hours a day but cannot cater for cash withdrawals or for cash
or cheque deposits. Issues arising from Internet banking include:
• Security. All banks are determined to make their online banking services safe
from inference and secure for customer details. Data encryption is used to secure
the data transfer between the customer’s computer and the bank’s computer.
• Changing nature of work. People working for the bank are not carrying out the
services provided by Internet banking. Banks require more people with
information technology skills and fewer people with banking skills.
106
Core
• Branch closures and job loss. With many customers using Internet banking,
EFTPOS and ATMs, there is less need to access the facilities provided by a bank
branch. This has resulted in branch closures and job losses.
Radio and video
The number of services delivered by the Internet is rapidly increasing. Two
examples of this development are radio and video. There are currently thousands
of Web sites broadcasting radio from around the world. These radio stations cater
for a variety of tastes. For example, it is possible to listen to a major sporting event
live on the Internet. In addition to the Internet providing radio services, there are
many Web sites with video.
Video on the Internet is replacing videotapes and other media. It allows
organisations to create unlimited video channels. These video channels are used
for sales, training, communication and a host of other purposes. Video on the
Internet saves time, reduces costs and provides the ability to view the video
globally. The size and quality of the video is currently less than that of a normal
television broadcast; however, it will improve with developments in technology,
such as increasing bandwidth.
ITITFact
Fact
A ‘mouse potato’ is an Internet user who spends an excessive amount of time
online and is addicted to the Internet. It comes from the term ‘couch potato’.
Working from home
Communication systems have led to an increase in the number of people who
either choose or are asked to work from home. This is called telecommuting.
Telecommuting is working at home and electronically communicating with the
office (see Figure 3.21). Even though working at the office is not likely to
disappear, advances in telecommunication are likely to make telecommuting more
common in the future. Factors that will
affect the future of telecommuting
include the availability of bandwidth,
the perceived value in telecommuting,
and the opportunities to work
collaboratively across large distances.
The Internet has provided the means for
a new type of organisation to develop
whose employees work almost entirely
through telecommunication with an
occasional face-to-face meeting.
The main advantages of telecommuting are greater flexibility in work
hours; saving money on transport,
clothing and food; and saving time. In
particular, it benefits people who are
physically impaired or required to look
after small children. The employer saves
on overheads, such as office space and
furniture. However, working from home Figure 3.21 Working from home.
107
can have its disadvantages. People can miss the social and professional contact
offered by an external place of work. They experience feelings of loneliness and
isolation. Telecommuting can also blur the distinction between work and home
life. The home is no longer a place where the pressures of work can be forgotten,
and work may be interrupted by domestic chores. There are many other issues
that arise when people work from home, such as:
• Is there going to be a greater investment in the equipment needed to cater for
telecommuters?
• Who is responsible for the maintenance of the equipment used in the home?
• Does the telecommuter have the same loyalty to an employer as an employee
working in an office?
• How secure are sensitive documents in the home?
Exercise 3.5
1
2
3
4
5
6
7
Why is there a danger of misinterpretation with messaging systems?
How are privacy and confidentiality a concern with messaging systems?
What is electronic junk mail? Why is it a problem?
Why are businesses establishing a Web site?
What is the effect of Internet trading on employment?
How are trade barriers affected by Internet trading?
Describe the method used by the IIA to deal with offensive material on the
Internet.
8 Describe three issues that have arisen from Internet banking.
9 Why is video used on the Internet?
10 Outline the advantages and disadvantages of telecommuting.
LEARNING ACTIVITIES
1 Outline some of the changes to the banking industry as a result of new
communication systems. Are these changes positive or negative? Give a reason for
your answer. How have these changes affected the nature of jobs in the banking
industry?
2 Alanna finds it convenient to shop on the Internet. However, she is concerned
about the issue of security. Explain why security is a problem. Describe two
measures that have been taken to overcome these security problems. Investigate
the issue of security by searching the Internet. Compare your results with another
student in your class.
3 ‘Information technology has resulted in people spending more time inside their
houses and less time exploring the world.’ Discuss this statement in terms of
developments in communication systems.
4 Communication systems are having positive and negative impacts on our society.
Briefly describe some of the changes to our society caused by communication
systems. What do you think is the greatest concern with communication systems?
Give a reason for your answer.
5 ‘Offensive material should be banned from the Internet.’ What is your view on
censorship of the Internet? Give reasons for your answer.
108
Core
Chapter review
PART A
1 Cyclic redundancy check is an error
detection method that:
A uses a division process
B counts the number of bits in a data
packet
C checks for redundant data
D performs a check in cycles
2 A seven-bit ASCII character 1001011
was sent with a parity bit of 1. The
character was received as the ASCII
character 1000011 and a parity bit of 1.
A Data was sent using an even parity
and interpreted as correct
B Data was sent using an even parity
and interpreted as incorrect
C Data was sent using an odd parity
and interpreted as correct
D Data was sent using an odd parity
and interpreted as incorrect
3 The baud rate is the:
A number of bits that can be transmitted in one second
B transmission of data at the same rate
C maximum number of data symbols or
electrical signals that can transmitted
in one second
D number of bauds that can be transmitted in one second
4 LANs often store application software
on more a powerful computer called a:
A Web server
B mail server
C file server
D print server
5 A person uses a debit card to purchase
goods in a shop. The transaction details
are transferred to the bank’s computer.
This data is protected during transmission by:
6
7
8
9
10
A a password
B protected transmission media
C data encryption
D a firewall
A combination of hardware and software to link two similar networks:
A bridge
B switch
C hub
D router
A data packet is sent through a LAN
to a terminal. The data packet passes
through each node until it reaches the
terminal or returns to the sender. The
network topology is a:
A star
B ring
C bus
D TCP/IP
XModem and ZModem are:
A file transfer protocols
B types of modems
C error checking methods
D network access methods
Each device in a network is called a:
A node
B terminal
C server
D workstation
The bandwidth, from lowest to highest,
is:
A fibre-optic cable, coaxial cable, microwave
B coaxial cable, microwave, fibre-optic
cable
C microwave, coaxial cable, fibre-optic
cable
D coaxial cable, fibre-optic cable, microwave
109
Chapter review
PART B
statement number.
Statements
1 A method of checking for errors in data
transmission using a division process.
2 A set of rules that governs the transfer
of data between computers.
3 A network topology that uses a central
computer with each device connected
directly to it.
4 The number of bits that can be transmitted in one second.
5 Data represented in the form of digits
or numbers.
6 An agreement that results in the exchange of information.
7 A method of checking for errors in data
transmission by counting the number of
bits in a data packet.
8 A central connecting device in a network.
9 It allows communication with other
people by storing and forwarding
spoken messages.
10 LAN access method that allows data
to be transmitted simultaneously to
all nodes on the network in both
directions.
11 It allows communication with other
users by sending and receiving electronic messages using a computer.
12 The maximum number of data symbols
or electrical signals that can transmitted
in one second.
13 A network topology where all devices
are attached so that the path is in the
shape of a continuous circle.
14 A device that directs data packets along
a path.
110
Core
15 Data represented by using continuous
variable physical quantities, such as
voltages.
List of terms
a analog
b baud rate
c bps
d checksum
e CRC
f digital
g email
h Ethernet
i
j
k
l
m
n
o
handshaking
hub
protocol
ring
star
switch
v-mail
PART C
following questions.
1 What is a communication system?
List the five basic components of a
communication system. Identify these
components when using email.
2 One method of error detection is parity
checking. How does this method work?
Describe one specific error that a parity
check would fail to detect.
following pairs of terms:
a Coaxial cable and optical-fibre cable
b Host computer and terminal
c Asynchronous and synchronous
d Error detection and error correction.
4 Briefly describe the three network
topologies.
5 Draw a diagram to explain the
communication link between two
computers. It should illustrate any
encoding and decoding that is carried
out by the link.
6 Identify a social and ethical issue
involved in a communication system.
Outline both the positive and negative
sides of the issue.
Options
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Transaction processing systems
Decision support systems
Automated manufacturing systems
Multimedia systems
4
chapter
TRANSACTION
PROCESSING
SYSTEMS
Outcomes
Overview
This chapter examines the characteristics of
transaction processing systems. It investigates
specific examples of real-time transaction processing and batch transaction processing. The
information processes of storing and retrieving,
collecting, and analysing for a transaction processing system are examined. The chapter
concludes by outlining the social and ethical
issues that relate to transaction processing
systems.
• demonstrates ethical practice in the use of
information systems, technologies and processes (H3.2)
4.1 Characteristics of transaction
processing systems
Transaction processing systems (TPSs) collect, store, modify and retrieve the
transactions of an organisation. A transaction is an event that generates or modifies
data that is eventually stored in an information system. Some examples of TPSs
are selling goods using a point-of-sale (POS) system, processing credit card
payments, or making a motel reservation. TPSs differ in character from other types
of information systems in that they directly support business operations. They
must be designed in conjunction with the organisation’s procedures. The transaction data obtained from a TPS is stored in an information system and processed
using a range of application software. It usually involves updating a database to
reflect changes to the transaction data.
The main information processes of a TPS are collecting and storage. If a TPS is
used to record a sale and generate a receipt, the transaction data is collected at the
POS terminal and then stored using an online database. The four important
characteristics of a TPS are rapid response, reliability, inflexibility and controlled
processing.
• Rapid response. Fast performance with a rapid response time is critical.
Businesses cannot afford to have customers waiting for a TPS to respond. The
turnaround time from the input of the transaction to the production of the
output must be a few seconds or less.
• Reliability. Many organisations rely heavily on their TPS. A breakdown will
disrupt operations or even stop the business. For a TPS to be effective, its
failure rate must be very low. If a TPS does fail, then quick and accurate
recovery must be possible. This makes well-designed backup and recovery
procedures essential.
• Inflexibility. A TPS wants every transaction to be processed in the same way
regardless of the user, the customer or the time of day. If a TPS were flexible,
there would be too many opportunities for non-standard operations. For
example, a commercial airline needs to consistently accept airline reservations
from a range of travel agents. Accepting different transaction data from
different travel agents would be a problem.
• Controlled processing. The processing in a TPS must support an organisation’s
operations. For example, if an organisation allocates roles and responsibilities
to particular employees, then the TPS should enforce and maintain this
requirement.
A TPS minimises the organisation’s costs by reducing the number of times that
data must be handled and by providing timely updates to the database. There are
two types of transaction processing: batch transaction processing and real-time
transaction processing
113
Batch transaction processing
Batch transaction processing collects the transaction data as a group, or batch, and
processes it later. It has a time delay. Transactions are collected and held for
processing until it is convenient or economical to process them. Waiting for a large
volume of data generally results in lower processing costs per transaction. The
transactions are collected and stored offline on a magnetic tape or on paper. The
time delay before processing or completing a batch run could be several minutes,
hours or even days. For example, the clearance of cheques is a batch process that
takes several days. Batch processing is used when a time delay will not decrease
the usefulness of the results. A batch approach is used for generating pay cheques
and other forms of paper output.
ITITFact
Fact
The term ‘batch’ originated when punch cards were the usual input
medium. A batch of cards represented a computer program and was stored
in sequence in a box. A computer operator fed the cards into the computer.
The output was obtained the next day.
Batch processing is carried out by large organisations using a mainframe or
mid-range computer (see Figure 4.1). It involves a large batch of an identical data
type, such as payroll or stock information. For example, a payroll application
collects data for each employee, such as the hours worked and overtime earned.
This data is processed in batches by updating a payroll master file. After the
master file is updated, the pay slips are created for all employees in the organisation. Batch programs are often run at night when there is less demand for
the information system. There are three disadvantages in batch processing:
• All processing must wait until a set time. The processing schedule is predetermined.
• Errors cannot be corrected during processing.
• Sorting the transaction data is expensive and time consuming.
Figure 4.1 Batch processing using a mainframe computer and magnetic tape.
114
Options
Batch transaction processing was the only feasible form of transaction
processing when data was stored on punch cards or tapes. However, advances in
information technology have resulted in the ability to do real-time transaction
processing.
Real-time transaction processing
Real-time transaction processing is the immediate processing of data. It provides
instant confirmation of a transaction but does require access to an online database.
Real-time processing involves using a terminal or workstation to enter data and
display the results of the TPS. It uses a computer network to link the terminals to
the mainframe computer and to access the online database. Real-time processing
involves a large number of users who are simultaneously performing transactions
to change data. Even though each individual user is processing a relatively small
number of records, their requests are being made at the same time. Two common
examples of real-time processing are airline reservation systems and banking
transaction systems.
ITITFact
Fact
Real-time transaction processing is often called OLTP (online transaction
processing). An online database is updated as the result of a business
transaction.
The two main concerns with real-time processing are concurrency and
atomicity.
• Concurrency ensures that two users cannot change the same data at the same
time. That is, one user cannot change a piece of data before another user has
finished with it. For example, if an airline ticket agent starts to reserve the last
seat on a flight, then another agent cannot tell another passenger that a seat is
available.
• Atomicity ensures that all of the steps involved in a transaction are completed
successfully as a group. If any step fails, no other step should be completed. For
example, a banking transaction may involve two steps: withdrawing money
from a cheque account and transferring it into a savings account. If the first
step (the withdrawal) succeeds, then the second step (the transfer) must
succeed; otherwise, the entire transaction is abandoned. This ensures that the
withdrawal isn’t recorded twice and the transfer only once.
Every real-time TPS has a user response-time delay caused by its transaction
processing activities. For a TPS to be classified as ‘real-time’, the response-time
delay must be acceptable for that application. For example, a computer system
controlling an aircraft guidance system requires a response time limited to a
fraction of a second. However, in an airline reservation system, a response time of
several seconds would be satisfactory. In this case, instantaneous access to any or
all of the data is either unrealistic or uneconomical. The main disadvantage
associated with real-time processing is the tremendous expense. Both the hardware and software costs of this type of processing exceed those of batch
processing.
115
Terminal
Terminal
Terminal
User Interface
TP Monitor
Application
DBMS
Database
Figure 4.2 Real-time transaction processing.
Transaction processing monitor
A transaction processing monitor (TP monitor) is software that allows the
transaction processing application programs to run efficiently. It manages the
sequence of events that are part of a transaction. A TP monitor provides a standard
interface between the input devices (such as terminals), the transaction processing
application programs, and the DBMS. It also provides data security by ensuring
that transactions do not get lost or corrupted. A TP monitor is used in conjunction
with a particular operating system.
Real-time and batch processing
There are a number of differences between real-time and batch processing. These
are outlined below:
• Each transaction in real-time processing is unique. It is not part of a group of
transactions, even though those transactions are processed in the same manner.
Transactions in real-time processing are stand-alone both in the entry to the
system and also in the handling of output.
• Real-time processing requires the master file to be available more often for
updating and reference than batch processing. The database is not accessible
all of the time for batch processing.
• Real-time processing has fewer errors than batch processing, as transaction data
is validated and entered immediately. With batch processing, the data is organised
and stored before the master file is updated. Errors can occur during these steps.
• Infrequent errors may occur in real-time processing; however, they are often
tolerated. It is not practical to shut down the system for infrequent errors.
116
Options
• More computer operators are required in real-time processing, as the
operations are not centralised. It is more difficult to maintain a real-time
processing system than a batch processing system.
Data validation
Data validation is used to check the entry of transaction data. It involves procedures to ensure that transactions are correct and have been accurately stored in
the database. Data validation involves transaction initiation and field checking.
• Transaction initiation is used to acknowledge that the TP monitor is ready to
receive the transaction data. It is used in real-time processing to eliminate a
number of possible errors. Some TPSs add an entry time to the transaction data
in an attempt to trace the data if it is lost.
• Field checking occurs when the transaction data is entered into a database. The
data is organised into files, records, fields and characters. Data validation is
carried out by checking the fields, using a range check, list check, type check or
check digit as described in Chapter 2.
Even though data validation is essential, it is impossible to validate all the data
in the system. For example, a user may incorrectly type ‘45’ instead of ‘54’. This
simple transposition is often difficult to detect. There may be no reason to
question this type of error.
Historical significance of transaction
processing systems
Transaction processing was the first type of information system. TPSs were used
during the 1950s when the electronic computer became available for business
use. The first commercially available electronic computer was called UNIVAC
(Universal Automatic Computer). It was designed by John Presper Eckert and
John William Mauchly. The first UNIVAC was delivered to the U.S. Bureau of
Census. It could process both numerical and alphabetical calculations with ease.
UNIVAC was used by organisations to batch process business transactions, such as
paying employees and recording customer purchases and payments. These initial
applications of a TPS are still important today.
Figure 4.3 UNIVAC.
117
Manual transaction systems
Manual transaction systems are business systems that operate without the use of
machines. People are used to record the data about the business activities. For
example, a manual POS system has eleven operational steps performed by a sales
assistant to sell a product to a customer:
1 Examine the product and determine the product price.
2 Record the product price on the sales slip and add it to the total price of all
selected products.
3 Repeat steps 1 and 2 for subsequent products.
4 Check the total price of all the products selected.
5 Inform the customer of the total price and wait for payment.
6 Receive payment for the products.
7 Calculate the amount of change owing to the customer.
8 Give the selected products, a copy of the sales slip, and the change to the
customer.
9 Repeat steps 1 to 8 for the next customer.
10 At the end of the business day, total all sales slips to check that the money
collected is correct.
11 Do a stocktake to count all products remaining. Check that the stock
remaining equals the stock at the beginning of the business day minus the
stock sold.
The manual POS system is typical of a manual transaction system. It is based
on a clear set of rules that is followed by a person. These rules, or procedures, in a
manual transaction system allow the system to be easily computerised. The
procedures that can be computerised are identified by the data they are processing. In the manual POS system, the data being processed is the price of
products sold and the receipt of payments. The manual procedures that collect,
manipulate and store this data (steps 1, 2, 4, 6, 7, 10 and 11) could be
computerised. A transaction is made up of steps 1, 2, 4, 6 and 7. These steps must
be completed before the transaction is considered successful. Steps 10 and 11
update the organisation’s financial position and its stock inventory. They verify
that the money collected and the remaining stock are correct. They give the
assurance that the business has not had any money or stock misplaced or stolen.
A stocktake is a simple procedure but very labour intensive when done manually.
Computerisation of a manual transaction system provides significant benefits
to the business. First, it increases the rate at which products are sold. There is less
time taken for a customer to purchase a product. Customers are not waiting for a
person to complete the manual procedures. A second benefit is that it provides
information on which products are in demand. The business knows what products
are selling from the inventory database. After a period of time, the business can
modify its range of products to suit its customers’ purchasing habits. Computerisation of a manual transaction system aims to maximise the profits of the
business. The design of a TPS should be based on detailed specifications of how
transactions are performed and how to control the collection of data. The
transaction data must be collected in a specific format and must match the
operation of the organisation.
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Options
Exercise 4.1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
What is a transaction processing system?
How do TPSs differ in character from other types of information systems?
Describe four important characteristics of a TPS.
What is batch transaction processing?
List three disadvantages of batch processing.
What is real-time transaction processing?
Explain the difference between concurrency and atomicity.
What is the main disadvantage associated with real-time processing?
Describe a TP monitor.
Why does real-time processing have fewer errors than batch processing?
Why are infrequent errors in real-time processing often tolerated?
List some ways in which data is validated in a TPS.
Why is it impossible to validate all the data?
When were TPSs first used?
Describe the benefits of computerising a manual transaction system.
LEARNING ACTIVITIES
1 Identify a batch transaction processing system. Describe the steps in its operation.
What information technology is used in this TPS? Distinguish between the storage
of the collected data and the storage of the processed data.
2 Identify a real-time transaction processing system. Describe the steps in its
operation. What information technology is used in this TPS?
3 Compare and contrast batch and real-time transaction processing.
4 Analyse an existing TPS and determine its strengths and weaknesses.
5 Search the Internet for information on UNIVAC. Describe its technical and physical
features. Why was the UNIVAC an important development for transaction
processing?
4.2 Examples of transaction
processing systems
In this section, we examine the components of a TPS and examples of real-time
transaction processing and batch transaction processing.
Components of a transaction processing system
People are an important component of a TPS. They can be classified as users,
participants, and people in the environment:
• Users of a TPS often take the data provided by the TPS and use it in another
type of information system. This is a main feature of a TPS. For example, a POS
system could provide stock inventory that is used by an automated
manufacturing system. The users of the other information systems belong to
the same organisation that owns the TPS. They are not interacting with the TPS
119
but are using the data provided by the TPS. Managers often take the data from
a TPS and use it in other information systems to make strategic decisions.
• Participants are the people who conduct the information processing. They are
the people who do the work. Participants need to know what to do, how to do
it and when to do it. They have an essential role in a TPS, and the success or
failure of the system is dependent on them. However, the credit for the success
of a TPS is often given to the information technology. Similarly, if the system
fails, it is reported as a ‘computer error’ even when the error is human, such as
entering the wrong data.
• People from the environment are becoming participants in real-time processing systems as they directly enter transactions and perform validation. For
example, when you withdraw money from an ATM, you are the participant of
a TPS. The transaction is performed using real-time processing. You enter the
data, such as account number, PIN and withdrawal amount. You also check and
validate the data at the ATM.
ITITFact
Fact
A transaction-processing designer (TP designer) is a person with the
responsibility for translating business requirements into a TPS that will
support the business.
Examples of real-time transaction processing
Three examples of real-time transaction processing are reservation systems, POS
terminals and library loan systems.
Reservation systems
Reservation systems are used extensively in any type of business involved in
setting aside a service or product for a customer to use at a future time. They are
commonly used for people who are travelling, such as making a motel reservation
or booking a seat on a train. These systems require an acceptable response time
because the transactions are made in the presence of the customers. Some
reservation systems automate decision-making functions, such as finding the flight
that best meets the customer’s needs. The steps for a typical motel reservation
system are as follows:
1 Answer customer enquiries about room availability and pricing for a certain
period.
2 Place a reservation on one or more rooms and receive confirmation of that
reservation.
3 Perform a cancellation of a reservation.
4 Take up the reservation on arrival.
5 Close off a customer’s account at the end of the stay and provide an invoice.
6 Perform consolidation activities, such as a ‘night audit’ in which transactions
for the day are posted to the general ledger.
7 Provide a report and information management functions.
120
Options
The motel reservation system is a TPS. It consists of participants, data/
information and information technology (see Figure 4.4). Steps 1 to 5 require realtime processing and are known as the ‘front office’ functions. Steps 6 and 7 are not
so critical and are known as the ‘back office’ functions. In most reservation systems,
the ‘front office’ is taken off line when the night audit is taking place.
The night audit performs such tasks as backing up the reservations database,
posting completed occupancy settlement transactions to the general ledger,
executing periodic reports, and updating the data used for occupancy calcu-lations.
The night audit is normally performed during the quiet business period, such as
between 1.00 a.m. and 3.00 a.m. Periodic reporting functions, such as costing
reports and occupancy reports, are scheduled during a night audit as they only need
to be run infrequently. The night audit is often done using batch processing.
Purpose
• Sell a room and other services
• Collect customer details
• Search database
• Update transactions
• Display room information
Participants
Data/
Information
Information
Technology
• Motel staff
• Confirmation
• Personal computer
• Manager
• Customer account
• DBMS
• Room details
• EFTPOS
• Receipt/reports
Information System
Figure 4.4 Motel reservation system.
121
Point-of-sale terminals
POS terminals are used by retail stores to sell goods and services (see Figure 4.5).
In large retail organisations, POS terminals send inventory data to a central
computer when the sale is made. The central computer is usually a mainframe or
mid-range computer that does the processing for the entire chain. If the POS
terminal immediately processes the transaction data, it minimises the costs of
batch handling. To accomplish this centralised processing of the transaction data,
the data is converted to a form that can be easily transmitted through a
communication system.
Purpose
• Sell goods and services
• Scan product
• Update product inventory
• Search database
• Display product information
Participants
Data/
Information
Information
Technology
• Store staff
• Barcode
• POS terminal
• Computing
personnel
• Product details
• Central computer
• Receipt
• Barcode reader
Information System
Figure 4.5 POS system.
One of the advantages of a POS terminal is that the correct price of the
product is received once the product number is entered. The product number is
usually entered using the barcodes on the product. Barcode readers are used to
read the barcodes and identify the product. Once the product is identified, the
POS terminal can provide the price and any other relevant information about
the product (see Figure 4.6).
122
Options
Customer
receipt
MIS
Server
UP
C/
qu
an
tity
Inventory
database
UPC
POS system
UP
tity
an
qu
C/
UPC
Price
Purchase
database
Inventory
report
Product database
Figure 4.6 System flowchart for a POS system.
Library loan system
A library loan system is used to
keep track of items borrowed from
the library. When a person borrows
a book, the librarian scans the
barcode on the person’s membership card and the barcode on the
book. This information and the
date are immediately recorded on
the library database. The library
loan system completes each transaction in real time. (See Figure 4.7.)
A library loan system has many
similarities with a reservation system. Its operational activities are
similar and involve keeping information on products, their availabilities, usage and maintenance. It
also shares the concepts of a ‘front
office’ and a ‘back office’ in which
activities are similar to a
reservation system. The only Figure 4.7 A library loan system.
significant difference is that the
library loan system has a larger number of items compared to the reservation
system. These items are often stored in a special database called a data warehouse.
123
Examples of batch transaction processing
Three examples of batch transaction processing are cheque clearance, bill
generation and credit card transactions.
Cheque clearance
A cheque is a written order asking the bank to pay a certain amount of money to
a particular person. When a cheque is issued to a person, he or she deposits it into
a bank account. However, the money cannot be withdrawn until the cheque has
been cleared. Cheque clearance involves checking that the person who wrote the
cheque has enough money in his or her account to cover the cheque. It usually
takes three working days. The cheques are cleared as a group during the bank’s
quiet period of the day. Cheque clearance involves batch processing.
Bill generation
Organisations create a bill, or invoice, for goods or services that have been
supplied to a customer (see Figure 4.8). They usually generate a group of bills at
a scheduled time. This enables the user to effectively manage his or her time
and results in less disruption to the main database. Bill generation is not done
immediately but as a group.
BQM
blast quarry maintenance
11 July 2000
TAX INVOICE
Peter CIANCIOSI trading as BQM
Milestone Mining Services
Mobile: 0414 00 44 22
24 Green Street
WOODSTOCK VIC 3751
ABN: 02 089466 721
Invoice Number: PC00015
Date
Work Carried Out
05-07-00
Workshop
XM-0515 Exhibition Centre Filters
3
5
$0084.00
$0140.00
$0092.40
$0154.00
06-07-00
XP-0879 Gauges Frankston
Change over Filters
Delivered Springs - EyeWise
Eppalock
Workshop
1
2
$0028.00
$0056.00
$0030.80
$0061.60
2
3
$0056.00
$0084.00
$0061.60
$0092.40
Workshop
Delivered Toggle - EyeWise
Eppalock
5
$0140.00
$0154.00
5
$0140.00
$0154.00
TOTAL HOURS
26Hrs
$3728.00
$3800.80
07-07-00
Hrs@$28 p/hr
Plus GST
(GST inc.)
Figure 4.8 Invoice.
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Options
Credit card sales transactions
Credit cards have become an important method of paying for goods and services.
Millions of such credit card sales transactions are completed every day. Some
are done at POS terminals, and some are done by taking an impression of the
customer’s credit card on a multi-page credit slip, which is then filled in by the
sales clerk. The retailer sends the credit slips to the bank in a group and does not
send each credit slip individually. Similarly, the POS credit card sales transactions
are not processed immediately but are stored for later processing. In either case,
credit card sales transactions are processed as a batch. Customers may view credit
card sales transactions, particularly those done at a POS terminal, as real-time
processing; but the actual updating is processed in a batch.
Exercise 4.2
1
2
3
4
5
6
7
8
9
Explain the difference between users and participants in the context of a TPS.
How are people from the environment becoming participants of a TPS?
Describe the steps for a typical motel reservation system.
Outline one advantage of a POS system.
Describe the procedures for a library loan system.
Compare and contrast a library loan system and a reservation system.
Describe the procedures for cheque clearance.
Why is bill generation done in a batch?
Describe the processing carried out in credit card sales transactions.
LEARNING ACTIVITIES
1 Real-time transaction processing systems perform information processes requiring
participants, data/information and information technology. Clearly identify the
participants, data/information, information technology and purpose of the
following TPSs:
a reservation systems
b point-of-sale terminals
c library loan system.
2 Batch transaction processing systems perform information processes requiring
participants, data/information, information technology and purpose of the
following TPSs:
a cheque clearance
b bill generation
c credit card sales transactions.
3 Describe the relationship between participants, data/information and information
technology for a POS system.
4 Construct a data flow diagram and a system flowchart to represent the following
TPSs:
a library loan system
b credit card sales transactions.
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4.3 Storing and retrieving
A TPS requires an efficient method for the storage and retrieval of data. Data is
stored in a database or a data warehouse. The data storage system requires welldesigned backup and recovery procedures.
Databases and files
The information processes in any large organisation are often unique and complex. The storage and retrieval of data must occur accurately many times each day.
Storage and retrieval depend on databases and files.
A database is an organised collection of data. An organisation stores all
accounting and operational records in a database, often called an operational
database. This database is a model of the organisation’s operational aspects. The
data in an operational database is defined in a schema. The TPS usually has a
restricted view of the operational database. For example, there is no need for an
order entry system to have access to the accounts payable data. This restricted
view, or subset, of the data is called a subschema. Databases are designed using a
hierarchical, network or relational structure (see Figure 4.9).
• A hierarchical database organises data in a series of levels. It uses a top-down
structure consisting of nodes and branches. Each node can have many branches,
but each lower-level node (child) is linked to only one higher-level node
(parent).
• A network database organises data as a series of nodes linked by branches. Each
node can have many branches, and each lower-level node (child) may be linked
to more than one higher-level node (parent).
• A relational database organises data using a series of related tables. Relationships are built between the tables to provide a flexible way of manipulating
and combining data.
Hierarchical structure
Network structure
Figure 4.9 Hierarchical, network and relational structures.
126
Options
Relational structure
When designing a database for real-time transaction processing, the following
features are important:
• Good data placement. A large number of users are simultaneously performing
transactions to change data. The database should be designed to access patterns
of data use and to place frequently accessed data together.
• Short transactions. Keeping transactions short enables the entire transaction to
be processed quickly, which improves concurrency. User interaction during
transaction processing should be avoided as this slows down the system.
• Real-time backup. Real-time processing is characterised by continuous operations with downtime kept to an absolute minimum. Backing up the database
needs to be scheduled during times of low activity to minimise effects on users.
• High normalisation. Redundant information is kept to a minimum whenever possible to increase the speed of updates and improve concurrency.
Reducing data also improves the speed of backups because less data needs to
be backed up.
• Archiving of historical data. Data that is rarely referenced should be archived
into separate databases or moved out of the heavily updated tables. This keeps
tables as small as possible, improving backup times and query performance.
• Good hardware configuration. The hardware needs to be able to handle a large
number of concurrent users and to provide quick response times.
A file is a block of data. In a database, a file is divided into a set of related
records. The records contain the specific information, such as details about a
customer or a product. Every TPS uses files to store and organise its transaction
data. Batch transaction processing and real-time transaction processing require
different types of files and different methods of storage and retrieval. In a TPS,
there are five basic types of files:
• A master file contains information about an organisation’s business situation.
The master file stores the operational database. Transaction data is stored in the
master file.
• A transaction file is a collection of transaction records. The data in the
transaction file is used to update the master file. Transaction files also serve as
audit trails and history for the organisation.
• A report file contains data that has been formatted for presentation to a user.
• A work file is a temporary file in the system used during the processing.
• A program file contains instructions for the processing of data. It is created
from a high-level programming language, such as Cobol, Fortran, Visual Basic
or C++.
Data warehousing
sources. Data gathered in real-time transactions can be used for analysis in an
efficient manner if it is stored in a data warehouse. A data warehouse provides data
that is consolidated, subject-oriented, historical and read-only:
• Consolidated. Data is organised using consistent naming conventions,
measurements, attributes and semantics. Organisations can use similar data in
different formats. For example, true or false data can be represented as
one/zero, on/off, true/false, or positive/negative. Data in the data warehouse is
stored in a single, acceptable format. Data warehousing allows data from across
the organisation to be effectively used in a consistent manner.
127
• Subject-oriented. A large amount of data is stored across an organisation. Some
of this data is irrelevant for executive reporting and makes querying the data
difficult. A data warehouse organises only the key business information from
operational sources so that it is available for analysis.
• Historical. Real-time transaction processing systems represent the current
value at any moment in time for various aspects of the business, such as the
stock inventory. They do not show the inventory at some time in the past.
Querying the stock inventory a moment later may return a different response.
However, data stored in a data warehouse is accurate for a specific moment in
time, as it represents historical information and cannot change. The data
warehouse stores a series of snapshots of an organisation’s operational data
generated over a long period of time.
• Read-only. After data has been moved to the data warehouse successfully, it
does not change unless the data was incorrect. The data stored in a data
warehouse represents a particular point in time; it must never be updated.
Deletes, inserts, and updates are not applicable in a data warehouse. The only
operations that occur in a data warehouse are loading and querying data.
Backup procedures
Organisations have become very dependent on their TPSs. For example, making a
reservation when the computerised reservation system is down is often impossible.
A breakdown in the TPS may stop the business. Well-designed backup and
recovery procedures minimise disruptions when the TPS goes down (see Figure
4.10). A backup is another copy of the data that could be used to rebuild the
system. If the system goes down, the recovery process rebuilds the system. The
success of backup and recovery depends on implementing appropriate procedures.
Backups are usually stored offsite or stored onsite in a fireproof safe.
Users
Transaction
data
Process
transaction
Data to
complete
transaction
Transaction
data
Transaction
data
Master
file
Database
Perform
backup
Transaction
file
Database
Updated
database
Backup
file
Database
Perform
recovery
Figure 4.10 A DFD showing backup and recovery.
128
Options
Transaction
data since
last backup
Recovery process
A TPS may fail for a number of reasons, such as system failure, human error,
hardware failure, incorrect or invalid data, program errors, computer viruses or
natural disasters. To cope with failures, the TPS must be able to detect and correct
errors. The recovery of a database involves the backup, journal, checkpoint and
recovery manager:
• Backup. Periodic backup copies are made of the entire database. Typically, a
backup copy is produced at least once a day. The copy should be stored in a
secure location where it is protected from loss or damage.
• Journal. Journals maintain an audit trail of transactions and database changes.
There are two basic journals, or logs. First, there is the transaction log. It records
all the essential data for each transaction, such as data values, time of
transaction and terminal number. The second kind of journal is the database
change log. It contains before and after copies of records that have been
modified by transactions.
• Checkpoint. The DBMS periodically suspends all processing to synchronise its
files and journals. All transactions in progress are completed, and the journal
entries are updated. The system is then said to be in a ‘quiet state’; and the
database, together with the transaction logs, is synchronised. The DBMS then
writes a special record to the transaction file. This special record is called the
‘checkpoint record’. The checkpoint record contains information necessary to
restart the system. A copy of the database up to the checkpoint record is
known as a ‘checkpoint copy’. Checkpoints should be taken frequently, such
as several times an hour. When failures do occur, it is often possible to resume
processing from the most recent checkpoint with only a few minutes of
processing work to be repeated.
• Recovery manager. This is a program that restores the database to a correct
condition and restarts the transaction processing.
The type of recovery procedure that is used in a given situation depends on the
nature of the failure. The general procedure involves restoring the data collected
from a backup device and running the transaction processing again. The two types
of recovery are backward recovery and forward recovery:
• Backward recovery is used to back out or undo unwanted changes to the
database. It is used to reverse the changes made by transactions that have
aborted. For example, a bank transaction involved transferring $100 between
two different accounts. However, failure occurred after the $100 was
subtracted from one account but before it was deposited to the required
account. Backward recovery involves the recovery manager restoring the first
account to its original value.
• Forward recovery starts with a backup copy of the database. It then reprocesses
the transactions in the transaction journal that occurred between the time the
backup was made and the present time. Forward recovery is much faster and
more accurate than backward recovery. Backward recovery involves the logic of
reprocessing each transaction, and this is very time consuming.
129
Magnetic tape
Magnetic tape is often used as a backup medium.
It can store large quantities of data inexpensively.
Magnetic tape is a very long, thin strip of plastic,
coated with a thin layer of magnetic material. The
tape is often wound on two reels inside a
cartridge. Tape is read from and written to using a
tape drive that winds the tape from one reel to
the other reel, causing it to pass a read/write head.
The main disadvantage with magnetic tape is that
it uses sequential access to retrieve data. This
form of access starts at the beginning of the tape
and reads all of the data until the required item is
found. Sequential access to data is slow, but
magnetic tape is a suitable medium for backup.
Magnetic tapes have a variety of sizes and formats,
such QIC tapes, DAT cartridges and 8-mm
cartridges. (See Figure 4.11.)
Figure 4.11 Magnetic tapes.
Grandfather-father-son
Grandfather-father-son is a backup procedure that refers to at least three
generations of backup master files. The most recent backup is the son, the second
last is the father, and the oldest is the grandfather. Grandfather-father-son is
commonly used with magnetic tape for a batch transaction processing system. If
failure occurs during a batch run, the master file is recreated by using the son
backup and restarting the batch run. This backup is one generation from the
master file. However, if the son backup is destroyed or corrupted, it is necessary to
go back another generation and use the previous backup (father). This process of
keeping several generations of backup files ensures that the data can be recreated
and not lost. Organisations often keep more than three generations. For example,
banks generally keep up to twenty generations.
Partial backups
Partial backups occur when only parts of the master file are backed up. The
master file is usually backed up to magnetic tape at regular intervals, such as
weekly or monthly. Transactions completed since the last backup are stored
separately and are called journals, or journal files. In the event of an accident, the
master file can be recreated from the backup tape and the journal files.
Updating in a batch
Batch transaction processing collects the transaction data as a group, or batch, and
processes it later. It has a time delay. Updating in a batch is used when transactions
are recorded onto paper (such as credit card slips) or stored on a magnetic tape.
Transactions are collected and updated in a batch when it is convenient or
economical to process them. Historically, updating in a batch was the only feasible
method when transaction details were stored on punch cards or magnetic tape.
The information technology did not exist to allow the immediate processing of
transaction data.
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Options
There are two stages in batch processing. The first stage is the collecting and
storage of the transaction data in a transaction file. It involves sorting the
data into sequential order. The second stage is the processing of the data by
updating the master file. This is not always a simple process. The updating of the
master file may involve data additions, updates and deletions that need to happen
in a certain order. If one error occurs in
the batch, then the entire batch is
rejected (see Figure 4.12).
Updating in a batch involves
sequential access. Sequential access
occurs when data is accessed in a
sequence. It is the only method of
accessing data stored on magnetic tape.
The steps in a batch update involve
retrieving the transaction data from a
Data entry
magnetic tape. A batch update starts at
the beginning of the magnetic tape and
reads all of the data in the order it was
stored. It is a time-consuming process to
locate a specific transaction on magnetic
tape. All previous transactions need to be
examined.
Daily transactions
The information technology in a
batch transaction processing system
requires a secondary storage medium that
Transaction file
can store large quantities of data
inexpensively.
Magnetic
tape
is
Batch run
frequently chosen for these reasons. The
software used to collect the transaction
data does not have to be online; and, if
necessary, the user interface can be
modified to suit the specific application.
Update
Master file
Figure 4.12 Batch transaction processing.
131
Updating in real time
Real-time transaction processing is the immediate processing of data. It provides
instant confirmation of a transaction. Real-time processing involves a large
number of users who are simultaneously performing transactions to change data.
It has resulted from recent advances in technology. Increases in the speed of data
transmission and improvements in bandwidth have made real-time transaction
processing possible. The steps in a real-time update involve sending the transaction
data to an online database in a master file (see Figure 4.13). The person providing
the information is typically available to help with error correction and receives
confirmation of transaction completion.
Data entry
Update
Daily transactions
Transaction file
Transaction data
Master file
Figure 4.13 Real-time transaction processing.
Data is accessed from a real-time transaction processing system using direct
access or random access. Direct access occurs when data is accessed without
accessing previous data items. It is much faster than sequential access, as the
previous data is not read. A direct access storage device stores data in a particular
storage location based on a mathematical procedure, or algorithm. It uses this
algorithm to calculate the approximate location of the data. If the data is not
found at this location, it searches through successive locations until the desired
data is accessed. Direct access often involves the use of an index and is called
indexed access. An index is a table that contains information about the location of
the data.
The information technology in a real-time transaction processing system
requires a secondary storage medium that can store large quantities of data and
provide quick access. Magnetic disk storage was developed to provide immediate
access to data. The software used to collect transaction data is online and has a
132
Options
user-friendly interface. The interface is very important, as a rapid response time is
critical. The turnaround time from the input of the transaction to the production
of the output must be a few seconds or less.
Exercise 4.3
1 Explain the difference between hierarchical, network and relational databases.
2 List six important features in the design of a database for real-time transaction
processing.
3 Describe five file types used in a TPS.
4 What is the purpose of a transaction file?
5 Describe the features of consolidated data in a data warehouse.
6 ‘Data stored in a data warehouse is accurate as it represents historical information.’ Explain this statement.
7 What is a backup?
8 Explain the difference between a transaction log and a database change log.
9 What is a checkpoint in the recovery process?
10 Explain the difference between backward recovery and forward recovery.
11 Why is magnetic tape often used as a backup medium?
12 Describe the process of using generations of backup master files for recovery.
13 What are the two stages in batch processing?
14 Describe updating in a batch that involves sequential access.
15 What are the steps in a real-time update?
16 Describe direct access of data from a real-time transaction processing system.
LEARNING ACTIVITIES
1 Relational databases are used for TPSs. They organise data using a series of related
tables. Briefly describe the following terms: schema, entity, attribute, relationship,
table and form.
2 The entertainment centre has set up a reservation system for all its events. The
system uses a relational database. There are three entities: Customer, Seats, and
Events.
– Customer: CustomerID, LastName, FirstName, Address, Suburb, PostCode,
Deposit and CreditCard.
– Seats: SeatNumber, EventID and CustomerID.
– Events: EventID, EventTitle, Date and Time.
a What would the primary key be for each entity?
e Populate the database with dummy data.
f Create four queries that would be relevant to this database.
g Create a report that lists all the customers and their seat numbers for a particular event. The report should be sorted on seat number in descending order.
h Apply backup and recovery procedures to protect this data.
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3 A relational database is used for a library loan system. There are three entities:
Book, Borrower and Transaction.
a List the attributes needed for each entity.
e Populate the database with dummy data.
f Create four queries that would be relevant to this database.
g Create a report that lists all the transactions on a particular date.
h Apply backup and recovery procedures to protect this data.
All information processes play a role in a TPS, including collecting and analysing
data.
Collecting
Collecting data for a TPS involves generating the transaction data. For example,
people using an ATM generate transaction data by entering their debit card
numbers and typing their requests on a keyboard. Collecting in transaction
processing involves the use of hardware and a variety of forms.
Hardware
Hardware used to collect data for a TPS includes MICR readers, ATMs and
barcode readers.
MICR (magnetic ink character recognition, pronounced ‘my-ker’) systems
are widely used by banks to read account numbers on cheques (see Figure 4.14).
Characters are printed using magnetic ink that contains magnetised particles.
Figure 4.14 Cheque with MICR.
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Options
MICR systems are designed to quickly and accurately read prerecorded data on
cheques and deposit slips. A MICR reader processes cheques at speeds of up to
2000 cheques per minute. The use of MICR for reading cheques is an example of
a batch transaction processing system.
An ATM (automatic teller machine) is a banking terminal that performs
common banking transactions, such as deposits and withdrawals. An ATM can be
used at any time during the day or night. When people complete a transaction
using an ATM, they are participants in a real-time transaction processing system. The ATM accesses a communication system. Data and information are
being transferred between an ATM terminal and the bank’s central computer in
real time.
Barcode readers are used extensively in retail industries to collect product
information at point of sale. Supermarkets use a laser to read barcodes (see Figure
4.15), and many businesses use handheld barcode readers. Product information
(description, price and code) is held on a central computer linked to the POS
terminal. Data about the item passing the barcode reader is collected quickly and
accurately. The description and price of the item is displayed on the cash register
and printed on the receipt. Libraries and many industries use barcode readers to
keep track of stock movements.
Figure 4.15 Barcode reader in use.
Forms
A form is a document used to collect data from a person. When the form is
completed, it is processed in a batch or in real time.
There are many different types of paper forms, such as a sign-on sheet for
payroll. A person completes the paper form, and the form is processed as a batch
at a convenient time. (See Figure 4.16.)
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Figure 4.16 A Medicare form.
On-screen forms are created for computerised data entry purposes to populate
fields in a database. The user can view, enter and change data in real time. (See
Figure 4.17.) For example, an airline ticket reservation system collects details of a
customer’s required flight via a form. A transaction is completed when the user
completes the form. A well-designed form provides information explaining the
Reservation code
005-3001.01
Book code
[USING MEDIAGRAM]
Book title
Required
inputs
Reserved date
03/01/00
Student ID
1710GLB
[AVRIL STARK]
Student name
OK
Figure 4.17 Data entry.
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Options
[10123]
Cancel
Verification
information
from system
required data and any rules that apply to particular fields, such as Sex (M/F).
Forms can minimise data entry errors by automatically filling in previously stored
data, such as a customer’s address, once the user has entered the customer’s name.
Web forms are typically used by users who wish to purchase items over the
Internet (see Figure 4.18). A form on a Web page may request relevant data, such
as items to be purchased, delivery address and method of payment. The data from
a Web form may be processed immediately (real-time processing) or at a later
time in a group of Web forms (batch processing). The responses from a Web form
become data in fields of a database.
Figure 4.18 Web form.
Analysing data
The results of processing transactions are stored in a database and are analysed in
many ways to meet the information needs of users. That is, the output from a TPS
is the input to other types of information systems, such as decision support
systems and management information systems.
TPSs flow through all aspects of an organisation and can provide the information
necessary to make informed decisions. Decision support systems (DSSs) assist
people to make decisions by providing information, models and analysis tools. For
example, a business uses a TPS to process its sales transactions. It uses a database
as a DSS to periodically summarise its sales data by date, region and product. This
summary information is stored in a separate database to be analysed by senior
management. To make decisions, management needs to be able to determine
trends in sales quickly by querying the data based on various criteria.
The amount of information available from TPSs is increasing at a staggering
rate. It has reached the point where people are being frustrated by information
137
overload. Data mining is used in DSSs to find relationships and patterns in the
data stored in a database. It sorts through the data and turns up interesting and
often useful connections. For example, data mining could be used to analyse the
transactions at the supermarket. It might determine whether there was a
relationship between tomato sauce sales and meat pie sales. This information
might be useful for marketing promotions. The information obtained from data
mining allows organisations to make more informed decisions about such topics as
improving marketing campaigns or siting a new store.
ITITFact
Fact
CICS (customer information control system, pronounced ‘kicks’) is a mainframe operating environment designed to enable transactions entered at
terminals to be processed concurrently.
Management information systems
Management information systems (MISs) provide information for the organisation’s managers. They present basic facts about the performance of the
organisation. Some common examples of MIS output are reports on sales,
stock inventory, payroll, orders and budgets. Information from an MIS is generally presented in report form. There are many different types of reports, such
as scheduled reports, forecasting reports, on-demand reports and exception
reports:
• Scheduled reports are standard reports provided on a regular basis. Middlelevel to low-level management uses these reports.
• Forecasting reports are used to help make projections about business trends.
These reports are important to the decision-making process. They are also
known as planning reports as they assist in the strategic planning of the
organisation. High-level management normally uses these reports.
• On-demand reports are generated on request and usually in response to a
specific need. They are generally requested by high-level management.
• Exception reports are used to alert management to unexpected or unfavourable situations that necessitate special handling. This type of reporting is
of interest to middle management.
The development of MISs and DSSs brought operations researchers and industrial engineers to the forefront of business planning. These information systems
require knowledge of an organisation and its activities in addition to technical
skills in computer programming and data handling. The key issues in designing an
MIS or a DSS include how a system will be modelled, how the model of the
system will be handled by the computer, what data will be used, and how far into
the future trends will be extrapolated.
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Options
Exercise 4.4
1
2
3
4
5
6
7
8
9
10
What are the advantages of using a MICR system?
Describe an ATM.
How are barcode readers used in retail industries?
What is an on-screen form?
How can forms minimise data entry?
Describe a Web form.
What is a decision support system?
What is the purpose of data mining?
Describe four types of reports used in management information systems.
What are the key issues in designing an MIS or a DSS?
LEARNING ACTIVITIES
1 A range of hardware devices is used in TPSs. Clearly describe the operation of the
following devices to collect data:
a ATM
b barcode readers.
2 Identify and collect three paper forms used in a TPS. Compare and contrast the
design of these forms. Will these paper forms be replaced by electronic versions in
the future? Give reasons for your answer.
3 Design a user-friendly form that could be used in a real-time transaction processing system, such as an airline reservation system. Describe the features that
make your form user-friendly.
4 Search the Internet for Web forms that would be used in a TPS. List the address of
three Web forms that follow good design principles. Compare your choices with
three students in the class. Determine the best Web form in your group.
4.5 Issues related to transaction
processing systems
Both positive and negative impacts arise from the use of a TPS. In this section, we
examine some of the issues raised by TPSs, such as the nature of work, noncomputer procedures, bias, the importance of data, and control in transaction
processing.
Nature of work
TPSs are changing the nature of work for many people. They essentially automate
business operations and hence will affect the people who perform these
operations. The automation of jobs and people from the environment completing
the transaction have affected the nature of work in many organisations.
Automation of jobs
Automation of jobs refers to the use of information technology to perform tasks
once performed by people. For example, the POS terminal has replaced many of
the tasks performed by people in a manual transaction system, such as memorising
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the price of products. Organisations are increasing their use of information
technology and TPSs. TPSs have allowed organisations to be more efficient and
offer a range of new services. However, they have contributed to many of the
changes in the workplace. Workers are required to learn new skills and complete
ongoing training. The automation of jobs often results in fewer people being
required to perform the same task. However, the loss of jobs in one industry is
often replaced by the job growth in another industry, such as the information
technology industry. The key ingredient is being retrained to perform new roles in
this growing industry.
People as participants
People from the environment have become
participants in TPSs as they directly enter
transactions. For example, when a person
withdraws money from an ATM, he or she is
the participant of a TPS (see Figure 4.19). The
effect of this change on the nature of work is
significant. An employee of the bank once
carried out the tasks completed by a person at
the ATM. This has resulted in fewer jobs in
banks. This issue is not restricted to banks. The
Internet is allowing people to become
participants in a range of TPSs. People are
purchasing an increasing range of products by
completing a Web form. They are bypassing a
range of people who provided this service at
the shop front. On the other hand, more
opportunities are being created in the
information technology industry to create this
user interface.
Figure 4.19 People as participants.
Non-computer procedures
Many organisations rely heavily on their TPS. When the computer is unavailable
due to a breakdown or other reason, non-computer procedures are needed to deal
with transactions in real time. For example, if the library loan system crashes, then
the librarian needs to have a non-computer procedure for customers to borrow a
book. When the computerised system is working again, the user needs a procedure
to enter the transactions completed by non-computer procedures.
Bias
Data needs to be free from bias. Bias means that the data is unfairly skewed or
gives too much weight to a particular result. It is rarely an issue in the collection
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Options
of data from a TPS, such as a POS terminal. This information process is carefully
designed and examined in many ways. However, the data gathered from a TPS can
be presented in a biased way using tables and charts. For example, tables can be
constructed without all the relevant data, and scales on charts can distort trends.
Some bias may exist in any explanation; however, it becomes an ethical issue
when the relevant information is knowingly misrepresented.
Importance of data
An organisation relies on its TPS and the data it processes. It is important for
organisations to have procedures in place to ensure that data is secure, accurate
and valid.
Data security
Data security involves a series of safeguards to protect the data. Data is under
threat of being stolen, destroyed or maliciously modified. There is a greater risk
when the data is accessible to multiple users in a real-time transaction processing
system. The first line of defence is to only allow access to data to authorised
people using passwords, personal objects and biometric devices. However, some
people are capable of evading these procedures. Further safeguards to protect data
involve data encryption and firewalls.
• Encryption is the process of coding data, and decryption is the process of
changing it back. It is the most effective way to achieve data security during
the transmission of data. Data is coded, transmitted, and then converted back
to its original form.
• Firewalls are used on networks to verify and authenticate all incoming data.
A firewall checks the password of anyone trying to access a network. Firewalls
are expensive to install and maintain. On large systems, more than one firewall
is necessary because barriers need to be placed at all critical points.
Data accuracy
Accuracy of data is the extent to which it is
free from errors. Data entered into a TPS is
not always accurate. Errors can be caused by
mistakes in gathering the data, mistakes in
data entry, a mismatch of the data and the
person, or out-of-date information. For
example, if the price of a product has been
entered incorrectly into the database, then
customers buying that product will be
charged the wrong price. This could be very
costly to the organisation. Opportunities
need to exist to check and change data if it is
wrong.
141
Data validation is used to check the entry of data. A well-designed TPS checks
each transaction for easily detectable errors, such as missing data, data values that
are obviously too high or too low, data values that are inconsistent with other data
in the database, and data in the wrong format. Data validation is carried out using
range checks, list checks, type checks and check digits as discussed in Chapter 2.
Data integrity
Data integrity describes the reliability of the data. It involves the accuracy,
currency and relevance of the data. Data integrity in real-time transaction
processing is provided when the transaction passes the ACID (atomicity,
consistency, isolation and durability) test.
• Atomicity occurs when all of the steps involved in a transaction are completed
successfully as a group. If any step fails, no other step should be completed. If
the first step succeeds, then the second step must succeed; otherwise, the entire
transaction is abandoned. If some operations succeed and others fail, there is no
atomicity.
• Consistency occurs when a transaction successfully transforms the system and
the database from one valid state to another. Consistency in a TPS stems from
the correct application programming, such as always debiting and crediting the
same amount.
• Isolation occurs if a transaction is processed concurrently with other transactions and still behaves as if it were the only transaction executing the system.
Transactions must not interfere with each other’s database updates.
• Durability occurs if all the changes that a transaction makes to the database
become permanent when the transaction is committed.
These ACID properties guarantee that a transaction is never incomplete, the
data is never inconsistent, concurrent transactions are independent, and the effects
of a transaction are permanent.
ITITFact
Fact
‘Acid test’ comes from the days when alchemists subjected metal samples to
strong acid to isolate the gold content. Today, it refers to rigorous testing.
Control in transaction processing
Controlling transaction processing starts with collecting and includes the way the
TPS manipulates the data and the way errors are corrected. Data preparation and
authorisation create the transaction data that will be entered into the TPS. People
in management positions of some organisations have created false transaction data
to promote their careers. Even though strict precautions are taken with data
preparation and authorisation, the results from a TPS are not always correct.
People should not become completely dependent on a TPS. They need to maintain
control over their organisation’s operations.
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Options
Exercise 4.5
1
2
3
4
5
6
7
8
9
10
What is the automation of jobs?
Describe some of the changes in the workplace as a result of automation.
How is the Internet allowing people to become participants in a range of TPSs?
Why are non-computer procedures needed in a TPS?
How is bias a problem in a TPS?
Explain the difference between encryption and firewalls.
Describe some of the ways inaccurate data is entered into a TPS.
What is data integrity?
What is the purpose of the ACID text?
Outline the issue of control of data in a TPS.
LEARNING ACTIVITIES
1 Identify three jobs that have changed as a result of TPS. Describe the implications
of these changes for participants of the system.
2 ‘The computerisation of transaction processing has resulted in people performing menial tasks. People are now not required to think.’ Comment on these
statements.
3 ‘The major concern for organisations in TPS is ensuring data is secure, accurate and
valid.’ Discuss this statement. Use the Internet to find information about data
security. Compare Australian and overseas data.
4 A friend has obtained access to a bank’s credit card transactions. Do you think
your friend is clever? Has your friend committed a crime? What would you do if
the friend deleted all your credit transactions for the past month? Describe the
penalty your friend should receive if he or she is caught.
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Chapter review
PART A
1 Which of the following is not an
important characteristic of a TPS?
A rapid response
B reliability
C flexibility
D controlled processing
2 Batch transaction processing is used for:
A generating pay cheques
B making an airline reservation
C buying a product at a point-of-sale
terminal
D borrowing a book at the library
3 Real-time transaction processing:
A has more errors than batch transaction processing
B does not require continuous access to
the master file
C is more difficult to maintain than a
batch transaction processing system
D processes transactions in a group
4 Data compared to a set of accepted
data is called a:
A range check
B list check
C type check
D check digit
5 Which of the following is not a feature
of data in a data warehouse from a realtime transaction processing system?
A a large amount of data is stored from
across an organisation
B data is stored in a single, acceptable
format
C data is current and contains the latest
transaction data
D data does not change unless the data
was incorrect
144
Options
6
7
8
9
10
A database that organises data using a
series of related tables is called a:
A hierarchical database
B relational database
C operational database
D network database
Updating in a batch usually involves:
A sequential access
B an online database
C direct access
D magnetic disk storage
Which of the following is not involved
in collecting data for a TPS?
A ATM
B MICR
C POS
D DSS
Which part of the ACID test ensures
that all of the steps involved in a
transaction are completed successfully
as a group?
A atomicity
B consistency
C isolation
D durability
The issue of bias is raised:
A during the collection of data
B to ensure people maintain control
over their organisation’s operations
C when data is gathered from a TPS
and presented using tables and
charts
D during the transmitting and receiving of data
Chapter review
PART B
statement number.
Statements
1 A database that collects information
from different data sources.
2 A copy of the data that could be used
to rebuild the system.
3 Collects, stores, modifies and retrieves
the transactions of an organisation.
4 Collects the transaction data as a group
and processes it later.
5 Involves the accuracy, currency and
relevance of the data.
6 Ensures that all of the steps involved in
a transaction are completed successfully
as a group.
7 Ensures that two users cannot change
the same data.
8 Occurs when data is accessed without
accessing previous data items.
9 The immediate processing of data.
10 Used in DSSs to find relationships and
patterns in the data stored in a database.
11 Used to check the entry of transaction
data.
12 Maintains an audit trail of transactions
and database changes.
13 Occurs when data is accessed in a
sequence.
14 At least three generations of backup
master files.
15 The use of information technology to
perform tasks once performed by
people.
16 The software that allows the transaction processing application programs
to run efficiently.
List of terms
a atomicity
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
automation
backup
batch transaction processing
concurrency
data integrity
data mining
data validation
data warehouse
direct access
grandfather-father-son
journal
real-time transaction processing
sequential access
transaction processing monitor
transaction processing system
PART C
following.
1 Outline the main differences between
real-time transaction processing and
batch transaction processing.
2 ‘Customers may view credit card sales
transactions as real-time processing, but
the actual updating is processed in a
batch.’ Comment on this statement.
3 Explain the meaning of the following
terms:
a transaction
b atomicity
c grandfather-father-son.
4 Describe the backup and recovery procedures for a TPS.
5 How is updating in a batch different
from updating in real time?
6 Data is important in a TPS. Briefly describe some of the procedures used to
ensure that data is secure, accurate and
validated.
7 Data integrity is provided when a transaction passes the ACID text. Describe
the four parts of the ACID test.
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5
chapter
DECISION SUPPORT
SYSTEMS
Outcomes
Overview
information systems that help users make
decisions. You will study examples of decision
support systems and learn to develop your
own decision support systems. Decision support
systems focus on the information processes of
organising, analysing and processing.
5.1 Characteristics of decision
support systems
The success of most human activities depends on the quality of the decisions.
Decisions are needed whenever a problem needs to be solved. Decision support
systems (DSSs) are information systems that assist users to make a decision by
providing information, models and analysis tools. They use a range of software
tools, such as databases, spreadsheets and expert systems. DSSs help decisionmaking by providing information using a model. A model is a representation of
some aspect of the real world, and a simulation is the use of that model. A model
may be a formula for calculating the cost of a new product to make a profit. A
DSS depends on the accuracy of the model.
ITITFact
Fact
‘Wetware’ is the term computer scientists use to refer to the brain’s
knowledge. Computer scientists are trying to find ways to connect human
brains to computers, so people can directly interact with them.
A DSS can be used on a daily basis or when an organisation has to make
changes or react to something unexpected. One example of a DSS is a system that
analyses the stock market and helps make decisions about shares. A DSS creates a
mathematical model of the variables affecting the decision, using statistical tools,
databases, spreadsheets and graphics. The model allows a manager to ask what-if
questions by changing one or more of the variables and seeing the projected
results. For example, the manager might ask what would happen if the share price
were raised.
Nature of decision support systems
The interactive nature of DSSs and the ability of the user to ask appropriate
questions are important factors in a DSS. Interactivity allows the user to choose
the sequence and content of the information to be displayed. It allows a DSS to
make decisions based on the data entered by the user. For example, a manager
wants to expand a business into a new product line. He or she enters the details of
the business’s current operations and an estimate of the effect of the new product
into a DSS. The DSS provides the information to assist the manager to make the
correct decision. The interactive nature of DSSs requires the user to have an
understanding of analytical tasks. If the user does not ask the right questions, it is
unlikely that the DSS will provide the right decision.
DSSs require the user to have an understanding of the problem and whether
using a DSS is appropriate. For example, taking a holiday requires a number of
decisions regarding time, place, transport, and accommodation (see Figure 5.1).
The user needs to understand the problem and all the factors that have an effect
on the decision. The difficulty of making a decision depends on the number of
conditions that have to be satisfied. A decision is easy to make when one option is
147
clearly better than another option. DSSs use three important information
processes:
• collecting—gathering data, such as facts, beliefs and ideas, that are related to
the problem
• organising—determining a method of organising data and selecting an
appropriate model
• analysing—selecting a course of action based on the information provided in
the previous steps.
Figure 5.1 Taking a holiday trip requires a number of decisions.
Components of a decision support system
Most DSSs have three components: data management, model management and
dialogue management (see Figure 5.2):
• Data management is used to collect and organise the data. For example, stockbrokers need access to share prices for past years. They use a database system
for data management. It maintains the data and provides a means for selecting
the required information. A DSS is often linked to external databases that are
used for other purposes, such as shipping, invoicing or daily transactions.
• Model management involves the use of a model to turn data into information.
People establish the relationship between quantities based on what they
observe and measure in real life. A model describes the relationship between
inputs, outputs and conditions. Models must be built and tested. There are
many types of models depending on the application, such as accounting
models to represent depreciation, tax planning or cost analysis. The validity of
the information obtained from model management is dependent on the
accuracy of the model.
• Dialogue management allows the user to enter a request in a convenient
manner. It provides the interactivity of DSSs. Dialogue management helps
the user to search large amounts of data, focus on relevant facts and apply
a model.
148
Options
Data Management
Retrieves and manipulates
relevant data
Model Management
Maintains alphanumeric
and graphical models,
formulas and algorithms
that are often used to
select the best model
Dialogue Management
Input tools (icons and
commands) accept
inquiries
Presentation tools
(tables and charts)
present analysed
information
Figure 5.2 Components of a decision support system.
Classifying situations
A DSS depends on the situation, the nature of data, the accuracy of the model
and the method of analysis. Situations are classified as structured, semi-structured
or unstructured.
Structured situations
Structured situations have decisions that are automated. The decision or solution
is reached using an algorithm. An algorithm is a series of steps that will solve the
problem in a finite time. In a structured situation, the steps are known and must
be followed in a certain sequence. For example, calculating the amount of carpet
needed for a room is solved using an algorithm. It uses a parameter (or a value of
data that may change), such as the width of the carpet or the dimensions of the
room. Structured situations always result in the same solution if the values of
the parameters remain the same. DSSs are not required in structured situations.
Semi-structured situations
Semi-structured situations follow a method to reach a decision, but the correct
decision is not guaranteed. The requirements of a semi-structured situation are
clear cut, but there are too many factors or some unknown factor that may affect
the decision. Experts in the fields of financial investment, weather prediction and
149
Figure 5.3 Weather forecasting, stock investing and horse racing are examples of
semi-structured decision-making.
horse racing believe that these are semi-structured situations. The experts’
knowledge allows them to obtain a manageable number of alternative solutions
but does not always result in the best solution. Some experts in a semi-structured
situation may reach a completely different solution. Most real-world situations are
semi-structured and can use a DSS (see Figure 5.3). A semi-structured situation is
a combination of a structured and an unstructured situation. It is neither clear cut
like a structured situtation nor unpredictable like an unstructured situation.
Structured Problems
Semi-structured Problems
How many workers are needed to fully
staff this production line?
What are the benefits of merging with
XYZ Inc.?
What is our optimal order quantity for
raw material, based on our production?
Where should we build the next five
stores of our retail chain?
How many turbines are needed to
supply power to this factory?
How will the consumer react if we lower
the price of our product by 10%?
Which of our regions yields the highest
revenue per salesperson?
What is the best advertisement
campaign to launch our new financial
service?
Which money market fund currently
yields the highest return?
What are the benefits of opening an
office in Paris, France?
How much would the implementation
of pollution-preventing devices cost us?
Which stock will yield the highest
return by the end of the year?
Table 5.1 Examples of structured and semi-structured problems.
Unstructured recognised situations
Unstructured recognised situations do not use a method to reach a decision. They
require judgement and insight into the problem. In an unstructured situation,
there is no algorithm to reach the best solution. There are too many factors or too
little knowledge about the situation. For example, people who buy shares with no
knowledge of financial investments are making a decision in an unstructured
situation. It is unpredictable. If the people used a financial adviser, their decision
would be based on a better judgement. However, the situation would still be
unstructured unless the financial adviser followed a method to reach a decision. In
unstructured situations, there is no single method to reach a decision and no
guarantee that the decision will be correct. It is dependent on intuition. DSSs are
used for unstructured recognised situations.
150
Options
Whether a situation is classified as semi-structured or unstructured depends on
the amount of knowledge and experience the user has in that area. For example,
a meteorologist would regard predicting the chance of rain tomorrow as a semistructured situation, while many people would regard it as unpredictable and an
unstructured situation. The development of DSSs that use artificial intelligence,
such as expert systems, have resulted in previously unstructured situations being
regarded as semi-structured situations.
Exercise 5.1
1
2
3
4
5
6
7
8
9
10
11
What is a decision support system?
List three types of software tools used in a DSS.
What is a model?
Why is interactivity an important factor in a DSS?
List the three components of a DSS.
Explain the difference between data management and model management.
What is the purpose of dialogue management in a DSS?
Explain the difference between structured and unstructured situations.
Describe a structured situation.
What is a semi-structured situation?
Why isn’t an algorithm used in an unstructured situation?
LEARNING ACTIVITIES
1 A DSS is used by a manager to employee a secretary. Decisions are based on
selection criteria, such as typing speed. List the criteria you would regard as
relevant for this DSS. How would you organise this data? Which criteria are the
most important? How could the DSS make decisions based on this information?
2 Describe a marketing situation that would benefit by using a DSS. Outline the
information technology needed by this system.
3 ‘The classification of situations into unstructured and semi-structured is dependent
on the user of the DSS.’ Do you agree with this statement? Give reasons.
4 Describe two situations that you would classify as:
a structured
b semi-structured
c unstructured.
5 Search the Internet for two examples of a decision support system. Describe the
characteristics of these systems.
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5.2 Examples of decision support
systems
DSSs assist users in semi-structured and unstructured situations. They are not
used in structured situations.
Semi-structured situations
Many decisions are made by people in semi-structured situations, such as a bank
officer deciding how much to lend a customer or a fingerprint expert doing
fingerprint matching.
Banking
Bank officers are involved in approving loans. This is a semi-structured situation,
as there are many different options for both the bank and the customer. The bank
has to assess the risk involved in lending the money. The bank officer collects data
about the customer’s financial status, such as the customer’s income and expenses.
The customer compares different types of loans and then makes a decision on the
most suitable loan.
A bank officer enters all the relevant data into a DSS. A list of loan options
allows the bank officer to compare different loans. The DSS assists by screening
the applicants and helping the bank officer to make a consistent decision in line
with the bank’s lending policy. It also provides advice to the customer on an
appropriate type of loan. Customers also have access to a range of software
to analyse loans, such as the Home Loan Analyser. This DSS allows the user to
compare different home loans from any lender and accurately estimate the total
cost of the loan.
Fingerprint matching
An automated fingerprint identification system
(AFIS) is used to help fingerprint experts to
match prints (see Figure 5.4). It is a database
system that is capable of matching prints and
searching at a rate of 2000 fingerprints per
second. An AFIS uses a combination of image
processing and matching algorithms to find a
match in a few seconds. Before AFISs, the manual
identification of fingerprints would have taken
hours or even days. It was a labour-intensive task.
Fingerprint experts had to be knowledgeable in
all areas of fingerprint identification. They
needed extensive knowledge to compare prints
and also had to know the procedures for locating,
processing and preserving prints.
An AFIS still requires an expert, as the AFIS
generates a list of possible matches. However,
advances in scanning, digital imaging and
matching algorithms have result in more accurate
Figure 5.4 Fingerprint.
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AFISs. These advances have resulted in experts seeing themselves as little more
than technicians. However, fingerprint matching still requires an expert to witness
all phases of fingerprint identification. The expert is required to make a decision
and use judgement regarding the degree of similarity between two prints.
ITITFact
Fact
The NSW Police Fingerprint Section was established in 1903 with 6000 sets
of fingerprints. Their automated fingerprint identification system was
established in 1986. It now uses a database containing 1.8 million sets of
fingerprints.
Unstructured situations
People make many decisions in unstructured situations, such as predicting stock
prices and managing disaster relief.
Predicting stock prices
DSSs are used to analyse stock prices and make decisions about shares. They often
store data on share prices in a database or a spreadsheet. DSSs use this data and a
model based on different parameters to predict future stock prices. Unfortunately,
predicting stock prices is an unstructured situation and unforeseen events occur.
A financial adviser may suggest certain shares to buy. However, this type of advice
is based on intuition and judgement. Financial advisers are usually very confident
about their advice but will never guarantee their decisions. DSSs in this situation
make use of spreadsheets, databases and neural networks.
Managing disaster relief
A disaster is a sudden, usually unexpected, catastrophe. In Australia, disasters
include fires, floods, earthquakes and cyclones. Disaster relief organisations respond after the diaster has occurred. They may use a geographic information
system (GIS). A GIS is an information system capable of assembling, storing,
manipulating, and displaying geographically referenced information (see Figure
5.5). It lets the user query or analyse a relational database and display the results
in the form of a map. A GIS has many uses besides disaster relief management,
such as weather forecasting, sales analysis and population forecasting. In a GIS, the
geographic information is described explicitly in terms of geographic coordinates,
such as latitude or longitude, or implicitly in terms of a street address.
153
Digitising of
existing maps
Multiple paper
products
GIS
Translation of
existing maps
Cartographic
database
Multiple digital
products
Figure 5.5 Components of a GIS.
Types of decision support systems
DSSs use a combination of spreadsheets, databases, expert systems and neural
networks to assist in decision-making.
Spreadsheets
A spreadsheet uses a rectangular grid made up of rows and columns to organise
and store data that requires some type of calculation. The results of these
calculations are often displayed in charts for analysis. Business people were the
first to use a spreadsheet to keep track of financial transactions and in stock
control. It allowed them to make decisions based on trends and to present data in
tables and charts. Today, spreadsheets are used by scientists, engineers and a wide
range of other people to assist in decision-making.
A spreadsheet creates a model using formulas to represent the real situation.
For example, a spreadsheet could be used to calculate loan repayments. It would
use a formula that relates the interest rate, time period and present value of the
loan. A spreadsheet helps with decision-making using a technique called ‘what-if’
predictions. ‘What-if’ is the process of making changes to the data and observing
their effects. For example, in the Best Books spreadsheet (see Figure 5.6), the user
could change the cost price and observe the effect on the profit.
The intersection of a row and a column in a spreadsheet is called a cell. The
position of the cell in the spreadsheet is called its cell reference (or cell address).
A range is a group of cells in a single row or column or in several adjacent rows
and columns. For example, the range B5 to C7 (written as B5:C7) contains the
data in cells B5, B6, B7, C5, C6, and C7.
A spreadsheet is very particular about the type of data that is entered into each
cell. It has three main types of data:
• A label is text entered into a cell to provide some explanation of the
spreadsheet. Calculations are not carried out using this data. Labels are used
for headings in rows and columns.
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= C5*1.5
= B5*D5
= B5*C5
= E5–F5
Formula
= SUM(G5:G10)
Label
Value
Figure 5.6 A spreadsheet for Best Books.
• Values are numbers stored in a spreadsheet on which calculations are carried
out.
• Formulas are instructions to perform a calculation. The answer to the
calculation will always appear in the cell that contains the formula. The
formula itself is not shown. The user can create a formula or select a function
such as AVERAGE. IF statements are combined with functions to allow
complex decision-making (see Figure 5.7).
= IF(OR(B6>10,C6>50),10*C6,0)
= IF(AND(B6>10,C6>50),200,0)
= D6+E6
Figure 5.7 A spreadsheet for Mick’s Music.
Spreadsheets have many features that make them easy to use and suitable for a
DSS. Some of the features include editing data, workbooks, templates, macros
and charts.
• Editing data is completed on the spreadsheet or using the formula bar. Cut and
paste, copy and paste, or drag and drop features are used to copy values, labels,
cell references and formulas into other cells. The ‘Fill Down’ or ‘Fill Right’
commands copy the contents of a cell into a range of adjacent cells.
• A workbook is made up of one or more spreadsheets called worksheets or
sheets. These sheets allow the user to organise related information in a single
file.
• A template is a document created for repeated use. A spreadsheet template
contains labels and formulas to solve a particular problem. The user enters the
values to obtain the required solution. A template saves time and effort.
155
• A macro is a series of commands stored in a file that can be executed by
pressing a few keys. Macros allow many operations to be performed automatically, such as opening menus, choosing commands or entering text. Macros
are used to create the dialogue management component of a spreadsheet being
used as a DSS.
• A chart is a graphical representation of numerical data. Charts convert data
in rows and columns into a picture that can be read at a glance. Charts make
data easier to understand. Trends are revealed, and comparisons can be made
instantly. Charts can assist people to make quick and accurate decisions.
Databases
A database is an organised collection of data. A flat file database organises data
into a single table and is suitable for many small applications. Flat file databases
organise data using data structures called files, records, fields, and characters. A
relational database organises data using a series of related tables. Relationships are
built between the tables to provide a flexible way of manipulating and combining
data. Relational databases are the most popular database structure.
Databases are an important component of most DSSs. They enable users to
access large amounts of data to make a decision. Retrieving data for decisionmaking usually requires the construction of a query. A query is a search of a
database for records that meet a certain condition. It is a question you ask of the
database. A query is constructed in the form: <Field name> <Operator> <data>.
The data in the query is often called the criteria. A common method for describing
a query is query by example (QBE). QBE requires the user to enter the criteria
against a field. A query language is a specialised language designed to search the
database. There are different query languages, each with its own grammar, syntax
and vocabulary.
sources. It is a storage area of raw data that can be analysed to assist organisations
to make decisions. A data warehouse involves careful planning to decide what data
to collect. The contents of a data warehouse are usually historical and fairly static.
A data warehouse is separate from the operational databases and is updated from
them at specified intervals. An enterprise data warehouse is a centralised store of
data from many different sources. It sells access to many different users for their
own analysis.
A data mart is a smaller version of a data warehouse. It is a store of data about
a specific topic or area. The emphasis of a data mart is on meeting the specific
demands of a particular group of users in terms of analysis, content, presentation,
and ease of use. Data marts may be part of a data warehouse, or they may be
created independently. Data marts allow users to get quick answers to their
queries.
Expert systems
Expert systems provide information and solve problems that would otherwise
require a person experienced in that field (an expert). They are designed for use
in highly unstructured settings, such as medicine and investment in shares. Expert
systems make a decision based on the knowledge of an expert. However, their
conclusions are not guaranteed. It is up to the user to accept or reject the decision.
The main advantage of expert systems is their low cost compared with the
expense of paying an expert or team of specialists.
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ITITFact
Fact
The concept of expert systems originated in the 1960s but first gained
prominence in 1977 when Edward Feigenbaum demonstrated the power of
an expert system to help with decision-making.
There are two important components of an expert system: the knowledge base
and the inference engine. The knowledge base is a set of general facts and if-then
rules supplied by an expert. Expert systems generate questions using the knowledge base and carry out reasoning using the inference engine. For example, a
medical expert system might use medical history, the patient’s symptoms and
laboratory test results to help doctors to diagnose infectious blood diseases and
prescribe antibiotics.
Neural networks
A neural network is an information system that works like the human brain and
is capable of learning. It contains a large number of processors connected like
nerve cells in the human brain. These processors, or nodes, form a network and act
like cells in the brain. A neural network finds relationships between sets of data to
develop an understanding of the situation. In an early demonstration, researchers
trained a neural network to read aloud. It learned to do this task by being shown
thousands of examples. Neural networks are very good at finding a link between
the data and a result. They are being used by:
• financial firms for economic forecasting and loan approval (see Figure 5.8)
• insurers to decide if a potential customer is a good risk
• marketers to predict which products will sell
• manufacturers to predict how much material they will need
• stockmarket firms to make predictions.
Input layer
Hidden layer
Output layer
Years at address
Approve loan
Years at job
Salary/loan
Health
Disapprove loan
Credit rating
Figure 5.8 A simplified neural network to approve or deny a loan.
157
ITITFact
Fact
In 1982, John Hopfield and several researchers at the California Institute of
Technology rejected the traditional concept of a computer with a CPU and
running a program. They built the first machines called ‘neural networks’.
Even though neural networks have been very successful, their applications are
still limited. Most neural networks contain a few thousand nodes compared to
about 100 billion nerve cells in the human brain. As a result, neural networks take
a very long time to train, and recognising visual images requires the processing of
large amounts of data. Neural networks are in the developmental stages, and
billions of dollars are being spent on research. Current applications of neural
networks include oil exploration, weather prediction and the exploration of
models of thinking and consciousness.
Exercise 5.2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
List two semi-structured situations where a DSS would be useful.
Describe a DSS used by a bank officer to approve a loan.
What is an AFIS?
What is the role of an expert in an AFIS?
List two unstructured situations where a DSS would be useful.
How does a DSS predict future stock prices?
What is a GIS?
List four types of DSS.
How does a spreadsheet help with decision-making?
Describe the type of data entered into a spreadsheet.
Describe the features that make spreadsheets easy to use and suitable for a DSS.
Why are databases an important component of most DSSs?
Explain the difference between a data warehouse and a data mart.
What are expert systems?
Describe the main advantage of an expert system.
What is a neural network?
Where are neural networks being used?
LEARNING ACTIVITIES
1 DSSs perform information processes requiring participants, data/information and
information technology. Clearly identify the participants, data/information, information technology and the purpose of the following DSSs:
a a bank officer deciding how much to lend a customer
b fingerprint matching.
2 Create a spreadsheet using the data in Figure 5.6. Save the spreadsheet with the
filename BOOKS.
a Best Books is aiming to make a profit of $1000 for Complete Idiot’s Guide.
What is the minimum number of units needed to be sold to make this profit
for this book?
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3
4
5
6
b Best Books is aiming to make a profit of $2000 for Mastering Spreadsheets.
What is the minimum number of units needed to be sold to make this profit for
this book?
c The selling price of each book is calculated by adding 50% to the cost price. Best
Books has decided to have a sale and decrease the markup on all books from
50% to 20%. What is the total profit using this markup if the sales figures
remain the same?
d The sale described in question (c) has resulted in an increase in sales of 30% on
all books. Add a new column after column B with a heading of ‘New sales’.
Enter formulas into this column to calculate the new sales figures. What is the
total profit based on these sales figures?
e What increase in sales is required to obtain a total profit of $7000? (Make your
answer correct to the nearest whole number.)
Create a spreadsheet using the data in Figure 5.7. Save the spreadsheet with the
filename MUSIC.
a Mick’s Music needs to determine the total bonus for all of its employees. Enter
a formula in cell F12 to calculate the total bonus.
b How much overtime does Sandra White need to complete to receive a total
bonus of $1400?
c What is the effect on the total bonus if the additional bonus is increased from
$200 to $250?
d What is the effect on the total bonus if the bonus and additional bonus are
calculated on 40 hours of overtime instead of 50 hours?
Michael is considering purchasing a restaurant in the local area. Each week the
restaurant buys $20 000 of stock for about 250 customers. This stock is sold at a
profit of 60%. The wages bill for the week is $9500, and Michael would need to
repay a loan at $5000 per month. Michael needs to analyse this data to determine
the restaurant’s profitability. Construct a spreadsheet to help Michael make his
decision and save it with the filename MICHAEL. What is the minimum number of
customers needed for the restaurant to break even?
Melissa works for a tourist bureau. She has been asked to collect and organise
data on popular Australian tourist destinations. The data collected includes the
location, cost, hours of operation, rating, amenities and characteristics. Develop a
database solution for Melissa using real or fictitious data and save it with the
filename TOURIST. Melissa needs to use the database to help with decisionmaking. Describe and demonstrate five different ways the database would help
Melissa make a decision.
The Internet contains many Web sites that use and promote a DSS. Describe the
features in two Web sites for each the following applications:
a predicting stock prices
b home loan analyser.
5.3 Organising and decision
support systems
Organising is the modification of data by arranging, representing and formatting
data. It is carried out after the data is collected. In a DSS, it involves designing
spreadsheets and constructing the knowledge base of an expert system.
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Designing spreadsheets
Designing spreadsheets involves creating a pen and paper model, identifying data
sources, planning the user interface and developing the formulas to be used.
Pen and paper
For centuries, people have used pen and paper to construct rows and columns of
numerical data and manipulate it in some way (see Figure 5.9). For example,
people used ledgers to keep records of their sales, incomes and payments.
Today, pen and paper are still used to plan a spreadsheet and create a
model of the situation. How is the spreadsheet going to solve the
problem? What data needs to be entered? How will I obtain the
data? What will the headings and titles be? How will the numbers
look? What is the relationship between the data? Does it
require a calculation? What formulas are to be used? What
results are required?
Creating a spreadsheet may also involve using a
template. A template is a document created for
repeated use. A spreadsheet template contains labels
and formulas to solve a particular problem. The user
enters the values to obtain the required solution.
For this reason, a template can save time and
effort. Templates are available in many spreadsheet
programs to help with decision-making.
Figure 5.9 A traditional pen and paper spreadsheet.
Data sources
Data is collected for a spreadsheet from a variety of data sources. It may be
obtained by researching the topic and selecting relevant facts. The Internet is a
source of data. Web sites and newsgroups present information on a range of topics.
Data sources may also include interviews, surveys, observations and measurements. Data should be gathered in an organised way to ensure nothing is omitted.
After the data is collected, it must be carefully interpreted to ensure that the
resulting information is valid. For example, can the results of a survey be
generalised to a large group of people? The reliability of the data source is another
issue. If similar data was gathered at another time and place, would the results be
the same?
User interface
A spreadsheet must be well-designed and easy to use. There is no correct way to
design a spreadsheet. Each particular problem has its own design requirements.
ITITFact
Fact
In a survey of blue-chip companies, more than 90% of large spreadsheets
contained at least one calculation error. Some spreadsheets were so badly
written they were impossible to test and had to be completely rewritten.
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However, a well-designed spreadsheet has four easily identifiable areas: instruction, input, calculation, and output (see Figure 5.10):
• Instruction area. The instruction area provides information about the spreadsheet or directions for use of the spreadsheet. It is usually at the top of the
spreadsheet and includes a title, a description, the authors and the creation or
revision date. Larger spreadsheets include a brief outline of their structure,
directions and parameters. A parameter is a variable that is given a constant
value for a particular application.
• Input area. The input area includes labels for headings and the values on which
calculations are based. The format of the values and labels is often completed
after the data has been entered. For example, when entering money values do
not include the dollar sign ($) as these values can be formatted as currency,
which will automatically enter the dollar sign. All inputs should be labelled
clearly so the user knows where and how to enter the data.
• Calculation area. The calculation area contains the formulas and functions that
complete the work of the spreadsheet. The calculation area is the heart of a
spreadsheet.
• Output area. The output area displays the result of the spreadsheet. In many
spreadsheets, the output area and the calculation area will be the same. All
outputs should be clearly labelled so the user understands the results.
Presentation of data should be suitable to the type of that data and its use.
Often a chart will display the information in a more understandable form for
a decision to be made.
Instruction area
Calculation area
Output area
Input area
Figure 5.10 A well-designed spreadsheet.
Formulas
A formula is an instruction to perform a calculation. Whenever values are
changed, the formulas are recalculated and produce new results. Formulas consist
of four main elements: numbers, cell references, operators and functions:
• Cell references allow formulas to refer to other cells in the same sheet or even
cells in other sheets. Cell references are often in the form of a range or name.
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A name is assigned to a cell reference or to a range to make the spreadsheet
easier to use. For example, in the formula =SUM(FirstQuarterSales), the
name FirstQuarterSales represents the range C20:C30 on the sheet named
Sales. It is easier to identify than =SUM(Sales!C20:C30).
• Operators are used to perform a process and are used to construct the required
formulas. Operators can be grouped as arithmetic, relational or text (see
Table 5.2).
Operator
Description
Example
+
addition
=6+2 gives 8
–
subtraction
=6–2 gives 4
*
multiplication
=6*2 gives 12
/
division
=6/2 gives 3
^
exponentiation
=6^2 gives 36
%
per cent
=15% gives 0.15
=
equal to
=3+2=4 gives FALSE
<>
not equal to
=22–1<>20 gives TRUE
<
less than
=22<20 gives FALSE
>
greater than
=22>20 gives TRUE
<=
less than or equal to
=15+4<=20 gives TRUE
>=
greater than or equal to
=15+4>=20 gives FALSE
text joining
=’A=’&FALSE gives A=FALSE
Arithmetic
Relational
Text
&
Table 5.2 Some spreadsheet operators.
• Functions perform a simple or complex calculation. Special rules or syntax
must be followed when functions are used. Functions consist of a function
name, such as SUM; one or more sets of parentheses (()); and arguments (see
Table 5.3). Arguments are the values on which the functions operate, such as
the range of cells B4:B8 in the formula =SUM(B4:B8).
Cell references make a spreadsheet very flexible. The value in a cell can be
changed and the results seen without having to change the formulas. This process
can be repeated many times, and it assists in decision-making. If a formula refers
to itself, either directly or indirectly, it is called a circular reference. For example,
if the contents of cell B4 were =B4+1, this would be a circular reference. It will
result in an endless loop, and an error message will be displayed. When a formula
is copied, the content of the formula in its new location may change or it may
remain exactly the same, depending on whether absolute referencing and relative
referencing was used to construct the formula:
• With absolute referencing (also called absolute addressing), the formula is
copied exactly, with the cell references remaining the same. Using the dollar
sign ($) in the cell reference (for example, $A$1) indicates that it is an absolute
cell reference. For example, if the formula =$B$5*$C$5 in cell D5 is copied to
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Function
Description
Example
ABS
absolute value
=ABS(–12) gives 12
INT
integer part
=INT(2.99) gives 2
LOOKUP
searches a range of cells for
for a lookup value
=LOOKUP(B6,A9:C14)
PI
mathematical constant
=PI()
ROUND
rounds to a number of
decimal places
=ROUND(3.14159,3) gives 3.142
SQRT
square root of a value
=SQRT(144) gives 12
SUM
adds up all the values in a list
=SUM(B4,B5,B6,B7)
AVERAGE
average of its arguments
=AVERAGE(2,4) gives 3
COUNT
how many numbers in the
list of arguments
=COUNT(5,1,12,5) gives 4
MAX
maximum value in a list of
arguments
=MAX(3,6,1,4) gives 6
MEDIAN
median (middle) of the given
numbers
=MEDIAN(8,3,10) gives 8
MODE
most common value
=MODE(4,6,6,4,4,4) gives 4
MIN
minimum value in a list of
arguments
=MIN(3,6,1,4) gives 1
STDEV
standard deviation
=STDEV(5,10,15) gives 5
AND
returns TRUE if all the
arguments are true;
returns FALSE if one or more
arguments are FALSE
=AND(2+2=4,2+3=5)
gives TRUE
=AND(2+2=5,2+3=5)
gives FALSE
FALSE
returns the logical value FALSE
=FALSE()
IF
returns one value if logical
test evaluates to TRUE and
another value if it evaluates
to FALSE
=IF(5<7,1,2) gives 1
=IF(8<7,1,2) gives 2
NOT
reverses the logic of the
argument
=NOT(1+1=2) gives FALSE
OR
returns TRUE if any argument
is TRUE; returns FALSE if all
arguments are FALSE
=OR(1+1=2,2+2=5) gives TRUE
=OR(1+1=1,2+2=5) gives FALSE
TRUE
returns the logical value TRUE
=TRUE()
Arithmetic
Statistical
Logical
Table 5.3 Some spreadsheet functions.
cell D6, the new formula is identical (=$B$5*$C$5) and the result of the
formula stays the same.
• With relative referencing (also called relative addressing), the mathematical
processes, such as the operators and functions, are copied but the cell
references change so that they relate to the destination. For example, if the
formula =B5*C5 in cell D5 is copied to cell D6, the new formula would
become =B6*C6. The cell references have changed relative to the destination.
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It is possible to have a formula containing both absolute and relative references. This is called a mixed cell reference. For example, if the formula
=LOOKUP(A5,$B$15:$C$22) in cell C5 is copied to cell C6, the new formula
would become =LOOKUP(A6,$B$15:$C$22) (see Figure 5.11).
= B5*C5
= LOOKUP(A5,$B$15:$B$22,$D$15:$D$22)
= LOOKUP(A5,$B$15:$C$22)
Figure 5.11 Spreadsheet showing a mixed cell reference.
Constructing a knowledge base
A knowledge base is a set of general facts and if-then rules supplied by an expert.
If the condition is true, then a certain deduction is made. For example, IF it has
4 legs, THEN it is a dog. This deduction would not always be valid. A more
accurate deduction is obtained by using a set of if-then rules. For example, IF it
has 4 legs AND IF it has a tail AND IF it barks, THEN it is a dog (see Figure 5.12).
Each if-then rule is combined using the AND operator or the OR operator.
When the AND operator is used, each condition must be true for the deduction
to be made. When the OR operator is used, only one of the conditions must
be true for the deduction to be made. For example, a knowledge base to screen
job seekers:
IF:
applicant_occupation NOT = "retired" AND
IF:
hours_worked > 12
THEN: applicant_status = "worker".
A knowledge base is often constructed using expert system shells (also called
shells). Expert system shells are a ready-made expert system except that they
contain no knowledge. When the knowledge is entered, it results in an expert
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Antecedent
Conclusion
IF
It has four legs
AND IF
It has a tail
AND IF
It has fur
It is a dog
AND IF
It barks
AND IF
It meows
It is a cat
Figure 5.12 With if-then rules, different combinations lead to different
deductions.
system. Shells provide an interface to assist the user in creating an expert system.
The shell queries the user for facts and for links between the facts. It enters this
data into the knowledge base. The majority of shells represent knowledge using ifthen rules. The shell displays the word IF on the screen, and the user enters the
conditions. The deductions (THENs) are added after the conditions (IFs). When a
set of if-then rules is completed, the shell builds a knowledge base and an inference engine. Expert system shells allow expert systems to be built very quickly.
The great majority of expert systems in Australia have been built using shells.
MYCIN is a famous expert system developed in the 1970s at Stanford
University in California. It was designed to assist non-specialist doctors in the
diagnosis and treatment of bacterial blood infections. MYCIN asks the doctor
about cultures grown from samples taken from the site of infection and the results
of other tests. The knowledge base about bacterial infections is coded in if-then
rules similar to following:
IF:
The stain of the organism is Gram-negative AND
IF:
The morphology of the organism is rod AND
IF:
The aerobicity of the organism is aerobic
THEN: The suggestive evidence is that the organism
is Enterobacteriaceae.
Exercise 5.3
1
2
3
4
5
6
7
List the questions answered using pen and paper to design a spreadsheet.
What is a template?
Describe some of the data sources for a DSS.
Describe the four main areas used in the layout of a spreadsheet.
List four main elements in a formula.
What is a ‘name’ in a spreadsheet?
What is a circular reference?
165
8
9
10
11
12
13
14
15
Explain the difference between an absolute and a relative reference.
What is a mixed cell reference?
What are if-then rules in a knowledge base?
Explain the difference between the AND and OR operator as they are applied in a
knowledge base.
Design a set of if-then rules to identify a cat.
What is an expert system shell?
What is the purpose of MYCIN?
What are the results of the following formulas:
a =8+2*5+7
b =9^2 + (24/6)
c =AVERAGE(8,12)
d =COUNT(6,2,14,7)
e =SUM(1,5,9,12)
f =MAX(8,5,1,9,8)
g =IF(6<12,5,10)
h =IF(13<12,5,10)
LEARNING ACTIVITIES
1 Create a spreadsheet using the data in Figure 5.11. Save the spreadsheet with the
filename ACE.
a Enter each employee ID from the lookup table into cells A6 to A12.
b Enter dummy data into cells B6 to B12 to represent the hours worked for each
employee.
c Copy the formulas in cells C5:E5 to cells C12:E12. Examine the formulas in cells
C6, D6 and E6. What changes have occurred?
d Todd Bradley is hired by Ace Technology. His employee ID is 945, hourly rate $14
and bank account number 7881225. Enter this data into row 23. Modify the
spreadsheet so that it will calculate Todd’s weekly wage.
e Ace Technology needs to determine the total weekly wage for all of its
employees and the average hourly pay rate per employee. Edit the spreadsheet
to do these calculations.
f What would the total weekly wage bill be if every employee worked 35 hours
a week?
g What would the total weekly wage bill be if every employee received an hourly
pay rate of $20?
2 Create a spreadsheet template that could be used as a personal budget for a Year
12 student. Save the spreadsheet as a template with the filename BUDTEMP. The
template is to contain possible sources of income and expenses. Formulas are to be
used to calculate total income and expenses and to balance the budget. Enter a
range of values. List five what-if questions that could be asked of the spreadsheet
for decision-making.
3 A video shop is having problems meeting its costs. It needs to decide whether it
should increase its rental prices. Design a spreadsheet model that could be used
to estimate the effects of different rental prices on revenue and the number of
rentals. Visit a local video store to obtain current price structures and typical
weekly rental numbers. Construct a well-designed spreadsheet. What will the
effect of increasing rental prices be?
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4 A person is eligible to drive if he or she is 16 years and 9 months old and has
passed a practical test and a theoretical test. Write down the if-then rules that
could be used in an expert system to determine whether a person is eligible to
drive.
5 An expert system is to be designed to assist a pet-shop owner to suggest a suitable
pet for a customer. Create a knowledge base of if-then rules that could be used in
the expert system. Design some test data to verify the rules.
6 Use an expert system shell to create a simple expert system. Choose a situation in
which you are the expert. Simple expert system shells can be downloaded from
the Internet.
5.4 Processing and decision
support systems
Processing in DSSs is the manipulation of data by editing it and updating it. This
section describes the structure of expert systems, how they deal with data and the
inclusion of certainty factors to handle unclear situations. It also includes a section
on macros as valuable tools in the processing of spreadsheet models.
The structure of expert systems
An expert system has four major components: a knowledge base, a database of
facts, an inference engine and an explanation mechanism.
Knowledge base
The knowledge base is a set of general facts and if-then rules supplied by an
expert. It is the heart of an expert system as it contains the detailed knowledge
supplied by an expert. The knowledge base is in the form of rules, such as if-then
rules. A knowledge base can contain just a few rules or thousands depending on
the scope of the expert system. The knowledge of an expert is expressed using the
if-then rules in the knowledge base.
Database of facts
The database of facts is the data that relates to the specific situation being
analysed. The database of facts is used by the inference engine when it is working
on a problem. It is simply a table. The database of facts holds the data about the
current task, such as the user’s answers to questions, data from outside sources,
intermediate results of the reasoning or conclusions reached so far. There is a clear
distinction between the knowledge base and the database of facts. The database of
facts contains data about the current problem. For example, a knowledge base to
predict sales would contain data from a range of different companies. However,
the database of facts would contain data from a specific company and its trading
performance.
Inference engine
The inference engine is the part of the expert system that carries out the
reasoning. It is a set of routines that carries out deductive reasoning by applying
the facts, assumptions, theories, and rules in the knowledge base. It carries out the
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reasoning by following a set of strict logical processes as opposed to the richness
of human reasoning. The inference engine applies the if-then rules in the knowledge base plus the database of facts to decide what question to ask next. It is
essentially a rule interpreter whose function is to use the if-then rules, facts and
other items in the knowledge base to solve the problem set by the user.
Explanation mechanism
The explanation mechanism is a method of checking how the expert system
inferred its deduction. Experts systems do not guarantee decisions; it is always up
to the user to make a final judgement. If users check the explanation mechanism,
they find out how a particular fact was inferred or why a particular question is
being asked. The explanation mechanism confirms the series of inferences that
have led to a conclusion or to a particular question being asked.
Types of inference engine
There are two main types of inference engines: forward chaining and backward
chaining.
Forward chaining
Forward chaining is an inference strategy in which the user supplies all the data
before the question is asked or the inference is made. It begins with data and
works forward to see if any conclusions can be reached. Forward chaining is often
used when there is no clear goal and the system is just attempting to determine all
of the conclusions implied by the data. For example, in forward chaining you
might be asked a series of questions about your eating habits. Forward chaining
then draws an inference or conclusion based on your answers, such as you have a
healthy diet.
Backward chaining
Backward chaining starts with one or more possible solutions and searches back
through the system to determine the questions to be asked. It is also known as
‘goal-directed reasoning’ or ‘conclusion-driven reasoning’. Backward chaining
starts with a tentative conclusion and searches back through the rules for the
questions or facts that support that conclusion. Backward chaining works in the
opposite direction to forward chaining. It starts with the tentative conclusion, such
as you are on a healthy diet, and then asks all the questions to ensure the user
meets the conditions (see Table 5.4).
Backward chaining
Starts from
Possible solutions
New data
Works towards
New data
Any conclusions
Progression through rules
Conclusions to conditions
Conditions to conclusion
Style
Conservative
Opportunisitic
Processing
Efficient
Possibly wasteful
User’s impression
Plodding but predictable
Responsive but quirky
Obvious usage
Selection between
alternative solutions
Building up solutions and
‘leaps’ in reasoning
Table 5.4 Comparison of backward and forward chaining.
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Options
Forward chaining
Backward and forward chaining have different uses and different effects.
Although they proceed in opposite directions, an expert system might use them
in combination. A doctor’s typical analysis process is a combination of forward and
backward chaining. The doctor starts with a brief medical history and draws some
tentative conclusions (forward chaining). The doctor then uses backward chaining
to confirm or deny the diagnosis (see Figure 5.13).
Forward Chaining
Bump on head
Head Injury
Vomited
Nausea
Disorientated
Dizziness
Suspect brain
haemorrhage
Backward Chaining
Perform CAT scan
Eliminate brain
haemorrhage
Figure 5.13 Forward chaining versus backward chaining.
Fuzzy logic
Fuzzy logic describes the variables that exist between a ‘true’ and a ‘false’. For
example, a piece of information might be ‘fairly’ true. Fuzzy logic seems closer to
the way our brains work. We combine data and form a number of partial truths on
many topics. Fuzzy logic is used in neural networks and expert systems.
The results of fuzzy logic operations may be expressed as probabilities or
possibilities. Fuzzy logic relies on historical data, mathematical probabilities and
rules. Consider this unclear situation: ‘If Stella is tired, then there’s quite a good
chance she’ll be in a bad mood’. The expert system must interpret the meaning of
the words ‘a good chance’. It does this by adding certainty values, or probabilities,
to the rule and attaching certainties to any new conclusions. Thus, fuzzy logic
might conclude that Stella is probably in a bad mood and that this conclusion has
a certainty value of 0.6.
Fuzzy logic is based on probability theory. However, it is much less rigorous
than probability theory and aims for a good guess rather than a precise probability.
The basic idea is to add certainty factors to rules and use these to calculate the
measure of belief in some deduction. Certainty factors are often based on the
rough guesses, or rules of thumb, of experts rather than on actual statistical
knowledge. They are easily updated if new information is received. The following
if-then rules have certainty values attached:
IF:
car won’t start
THEN: battery is flat (certainty value = 0.7)
IF:
car won’t start
THEN: starter motor is broken (certainty value = 0.2).
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The certainty values in the example are based on the expert’s knowledge or
guess about how often flat batteries are the cause of a car not starting versus how
often broken starter motors are the cause.
Macros
A macro is a series of commands stored in a file that can be executed by pressing
a few keys. Macros allow many operations to be performed automatically, such as
opening menus, choosing commands or entering text. Macros save time and
reduce keyboard errors. Any sequence of actions that a user performs can be
recorded as a macro. For example, your name may appear in all your spreadsheets.
If you store your name in a macro assigned to the ‘F2’ key, then every time you
press the ‘F2’ key, the macro will type your name.
To record a macro, select the ‘Record New Macro’ command. The command
will ask for a name for the macro so it can be saved as a file and will ask which key
or keys to assign the macro to. After you enter a name and key assignment, the
macro recorder starts working. Each action that you complete will be
remembered. Do the task that the macro will perform. When all the actions are
completed, turn off the macro recorder by selecting the ‘Stop Recorder’
command. The macro is used by selecting the ‘Run Macro’ command. This
command will carry out all the actions stored in the macro. Macros are used
to automatically move to specific areas of the spreadsheet, to sort data areas or to
format areas. Macros can also be created using programming languages, such as
Visual Basic.
Exercise 5.4
1
2
3
4
5
6
7
8
9
10
11
List the four major components of an expert system.
Explain the difference between a knowledge base and a database of facts.
What is an inference engine?
How is the explanation mechanism used in decision-making?
What is forward chaining?
Describe a situation that combines forward and backward chaining.
What is fuzzy logic?
What is a certainty value?
How is fuzzy logic calculated?
What is the meaning of a conclusion with a certainty factor of 0.2?
How do you record a macro?
LEARNING ACTIVITIES
1 A person’s results from a series of tests, such as running up stairs or throwing a
ball, are entered into a sports expert system. The expert system then suggests the
most appropriate sport for that person.
a Describe the type of information held by the knowledge base. Your answer
should include some if-then rules.
b Describe the type of information held by the database of facts.
c Do you think the expert system is using forward chaining or backward chaining?
Justify your answer.
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Options
2 Sarah is prepared to invest somewhere between $3000 to $15 000 in a financial
institution. Investigate the current interest rates for a term deposit at three
different financial institutions. Sarah needs to make a decision on the amount of
the investment and the length of her investment.
a Construct a spreadsheet with clearly defined instruction, input, calculation and
output areas. Save the spreadsheet with the filename SARAH.
b Create a simple macro to automatically move to each specific area of the
spreadsheet.
c What is the effect of different interest rates on her investment? If you had this
amount of money, where would you invest it? Estimate the return for your
investment and include it on the spreadsheet.
3 How can backward chaining be used to draw conclusions in an expert system
based on the following set of rules:
If wage > $50 000, then wage is good.
If assets > $120 000, then credit risk is good.
If wage is good and credit risk is good, then grant loan.
4 An expert system uses the following if-then rules: IF has-spots(X) AND has-fever(X),
THEN has-measles(X). Certainty factor is 0.5. What is the meaning of the fuzzy
logic in this situation?
5 Name three situations where fuzzy logic needs to be applied. Describe these
situations using if-then rules and attach certainty factors to the conclusions.
6 ‘Intelligent enterprise’ is a rapidly growing aspect of the Internet. Search the Web
to obtain information on this topic. (Try www.intelligententerprise.com.)
5.5 Analysing and decision
support systems
Analysing in a DSS is the interpretation of the data. It involves examining the data
and giving meaning to it. This section looks at methods of extracting relevant
information from spreadsheets and databases. It also compares and contrasts the
different methods of matching data used by databases, neural networks and expert
systems.
Data mining
Data mining is a process that finds relationships and patterns in the data stored in
a database. It sorts through the data and turns up interesting and often useful
connections. Intelligent agents are pieces of software used in data mining to search
through relational databases for relevant data. For example, data mining could be
used to analyse the transactions at the supermarket. It might determine that there
was a relationship between tomato sauce sales and meat pie sales. This information
might be useful for marketing promotions. The main purpose of data mining is to
identify new marketing opportunities and to target particular niche markets.
However, one problem with data mining is that many of the patterns occur by
chance and have no value in making decisions. Data mining also raises issues of
privacy and ownership of data.
Data mining identifies patterns in data and infers rules from these patterns. It
then uses additional data to refine the rules based on the original patterns of data.
Results from data mining include:
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• linking a number of events together, such as linking two mandatory courses so
they are timetabled at different times
• identifying patterns, such as a sequence of courses over a number of years that
students commonly choose
• organising data into patterns, such as the length of degree
• inferring rules from certain subgroups that distinguish them from other groups,
such as groups based on age or interest.
Internet search engines, such as AltaVista, provide data mining tools to assist
with finding information on the Internet. These sites maintain large databases of
information about Web pages. Their search engines have Web crawlers that search
the Web and group sites into classifications. Users can search for relevant Web sites
by using the classifications and subject headings.
ITITFact
Fact
Search engines are a relatively ancient technology. In the 1970s, a search
engine was used by IBM to search voluminous text files created by lawyers
defending IBM against a U.S. Government anti-trust suit.
Extracting summary data
The purpose of a spreadsheet is to produce information in a useful form to assist
decision-making. It changes data into information by performing calculations.
However, information is difficult to understand when too much information is
presented or it is in the wrong format. Extracting summary data from a
spreadsheet may involve using a range of different tools:
• Filtering data so that it will display only the desired data. For example, a
spreadsheet of international sales data can be filtered to only show the
Australian sales data. Extracting summary data is often easier if the data is
sorted.
• A report allows you to insert headings and titles and choose the information to
be printed. Spreadsheet programs allow the user to prepare more than one
report from the same spreadsheet.
• A pivot table is an interactive table that quickly summarises large amounts of
data. The user specifies the data and the calculations to be performed. When
the table is built, it is possible to rotate the rows and columns to see different
summaries. This ability to pivot the dimensions of the table makes it a very
powerful tool. Pivot tables are linked to the original data in the spreadsheet.
Spreadsheet analysis
Spreadsheets are analysed in many different ways to obtained information and
help with decision-making. Three of these methods are what-if models, statistical
analysis and charts.
What-if models
A what-if model, or sensitivity analysis, is the process of making changes to the
data and observing their effects. For example, in a budget spreadsheet, the user
could change one of the expenses and observe the effect on the balance (see
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Options
Figure 5.14). Most spreadsheet programs allow data from other sources to be
used. Data can be imported from relational databases or even from the Internet.
This allows different sets of data, or scenarios, to be used within the same
spreadsheet model. For example, in the budget spreadsheet the user could use a
new sheet for each family member. Each sheet would have a set of values for that
person. The ‘what-if’ analysis is then performed using a combination of the data
in each sheet.
Figure 5.14 Spreadsheet used for what-if questions.
Statistical analysis
Spreadsheet programs contain many built-in statistical functions. Statistical
functions are used to analyse and interpret data. Table 5.3 on page 163 describes
seven statistical functions commonly used in a spreadsheet for statistical analysis,
such as STDEV. Statistical functions are often used to construct statistical models
that perform complicated analyses, such as analysis of variance or regression
analysis. A linear regression model is the best-fit relationship between two types
of data, such as sales and money spent on marketing (see Figure 5.15). An
organisation might develop a linear regression model to estimate future sales
based on past experience.
Charts
A chart is a graphical representation of numerical data. Charts convert data in
rows and columns into pictures that can be read at a glance (see Figure 5.16). Text
and tables require close study to obtain a general impression of a subject. Charts
make data easier to understand: trends are revealed and comparisons are made
instantly. Charts can help people make quick and accurate decisions. There are
many different types of charts, including bar, column, line and pie charts:
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ne
li
nd
Tre
40
35
Advertising
($M/month)
Sales
($M/month)
1.1
20.3
Sales ($ million/month)
30
1.3
21
25
1.2
20.1
20
1.5
22.7
15
1.4
21.9
1.4
22
2.5
32
2.8
36
2.8
35
2.8
34.8
10
5
0
1.1
1.3
1.2
1.5
1.4
1.4
2.5
2.8
2.8
2.8
Advertising ($ million/month)
Figure 5.15 A linear regression model for predicting sales volume.
Cost
• A bar chart allows comparisons between items to be made at a glance and
shows variation over a period of time. A bar chart presents data in horizontal
rectangles. The length of the rectangle gives a visual representation of its value.
In bar charts, numeric values are plotted along the X-axis, and categories are
plotted along the Y-axis.
• A column chart also allows comparisons between items to be made at a glance
and shows variation over a period of time. A column chart presents data in
vertical rectangles, and the length of each rectangle gives a visual representation of its value. In column charts, categories are plotted along the X-axis,
and numeric values are plotted along the Y-axis.
• A line chart shows trends or changes in data over a period of time. It emphasises
time flow and rate of change rather than the amount of change. A line chart
presents data by joining a line between adjacent values. Each value is plotted as
a dot called a data marker or data
Warehouses against location
point. In line charts, categories are
7000
usually plotted along the X-axis,
and numeric values are plotted
6000
along the Y-axis.
Distance
5000
• A pie chart shows the relationship,
or proportions, of parts to a whole.
4000
Pie charts appeal to people
Hour & cost
because they are easy to read and
3000
attractive. A pie chart presents data
as sectors of a circle. Sectors of a
2000
circle are similar to slices of a pie.
1000
0
1
2
3
Warehouses
Figure 5.16 Charts convert data into pictures
that can be read at a glance.
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Data matching
Data matching involves finding data and giving some meaning to it. DSSs use
different ways to match data in a database, a neural network and an expert system.
Data matching in:
• a database involves searching and sorting data. It requires the user to construct
an appropriate query and interpret the results. Data matching in a data
warehouse is achieved using data mining. It finds relationships and patterns in
the data stored in a database.
• a neural network is achieved by finding relationships between sets of data to
develop an understanding of the situation. Neural networks are capable of learning. They examine the data and create new information as they are training.
• an expert system involves the use of a knowledge base, a database of facts and
an inference engine. The knowledge base and database of facts contain all the
data, and the inference engine carries out the reasoning by using the facts,
assumptions, theories, and rules.
Both the database and the expert system have a fixed body of data, unlike the
neural network whose learning may create more data and information. However,
this distinction is blurring. For example, many recent expert systems have a neural
network component to allow them to learn. In addition, data mining used in data
warehouses applies many of the techniques from neural networks to discover new
information.
Exercise 5.5
1
2
3
4
5
6
7
8
What is the purpose of data mining?
Describe four results obtained from data mining.
List three tools for extracting summary data from a spreadsheet.
Why is data filtered?
What is a pivot table?
List three ways that spreadsheets can be analysed.
What is a linear regression model?
Describe the four different types of charts that are commonly used to display
information.
9 What is data matching?
10 How is data matching achieved in a neural network?
11 Explain a distinction in data matching between the database and expert system
compared to a neural network.
LEARNING ACTIVITIES
1 Create separate spreadsheets and an appropriate chart for the following data:
a Compare sales figures over two days at the following stores to show any
variation over time: Castle Hill, $15 000 and $13 000; Rose Bay, $17 000 and
$18 000; Parramatta, $23 000 and $26 000; and Campbelltown, $12 000 and
$10 000.
b Show the proportions of parts to the whole for the following age groups: 0 to
20, 36%; 20 to 40, 26%; 40 to 60, 24%; and 60 to 80, 14%.
c Analyse each of the above spreadsheets and draw a conclusion based on your
analysis.
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2 Michelle has accepted a position as a librarian. She is moving away from home and
concerned about her finances. Develop a spreadsheet to analyse Michelle’s
finances. Michelle will receive $40 126 per annum (before tax) as a librarian and is
paid fortnightly. She has $4500 invested in a bank, and interest is paid half-yearly.
Michelle wants to purchase a car and needs a personal loan of $30 000 from a
bank. Payments will be paid monthly for five years. Michelle needs to budget for
the following expenses: rent, food, utilities, clothing, entertainment, car
repayments and savings. She is hoping to save some money for a holiday at the
end of the year. Investigate your local community to obtain appropriate living
expenses, then:
a Design a spreadsheet for Michelle’s finances. Save the spreadsheet with the
filename MICHELLE.
b Use some of the statistical functions to analyse the spreadsheet.
c Construct appropriate charts to help analyse the spreadsheet.
d Create some what-if models and draw a conclusion based on your analysis.
All information processes play a role in decision support systems, including
collecting and storing and retrieving.
Collecting
Collecting is the information process that involves deciding what to collect,
locating it and collecting it. In DSSs, it involves identifying data and identifying
the roles of the expert and the knowledge engineer in the creation of expert
systems.
Identification of data
When collecting data for DSSs, it is important to know what decisions you have
to make. This determines whether the source of data is primary or secondary.
Primary source is when data is collected first hand. Many organisations generate
their own primary source data because they consider it more meaningful and
reliable, although it is time consuming and costly. Data from primary sources is
acquired through interviewing people, conducting surveys and questionnaires, or
observing the system in operation. Secondary source is when data is collected or
created by someone else, such as data collected from newspapers, books, other
print media, electronic databases, CD-ROMs and the Internet. This is often the
quickest and least costly method of collecting data, but it may be less meaningful
and reliable than primary source data.
After the data is gathered, it is often classified as structured or unstructured.
Structured data is predefined characters, usually numbers, whose meaning and
format is specified. It is easily stored and retrieved in an orderly manner for
decision-making. Spreadsheets and many databases use structured data. Unstructured data does not fit a predefined or descriptive model. It includes all types of
media, such as text, audio, numbers, images and video. Unstructured data is more
difficult to use in DSSs as it creates greater processing and storage demands.
When collecting data for DSSs, users should consider the data range, time span
and level of detail. The data range is the amount of data and the number of
sources. To make a strategic decision, management may need a wide range of data,
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Options
such as the average monthly amount spent on advertising over the last ten years
by companies in the same industry. Although the required information is only one
number, it is derived from vast amounts of data from many organisations over a
long time period. This data would have a broad data range, a wide time span (ten
years) and a low level of detail (one number).
The role of the expert
Expert systems collect data from a person experienced in that field, or an expert.
The expert supplies the knowledge for the knowledge base and the inference
engine. The quality of an expert system is dependent on the knowledge of the
expert. Expertise is the skill and knowledge, generally gained by experience, that,
when applied to a problem, results in a performance well above the normal.
Expertise often consists of large amounts of factual information that is applied
using specific rules to analyse a problem in an efficient manner. Most rules that
experts use are heuristic. Heuristic rules require more than ordinary knowledge;
they are put together from the experts’ experience and hindsight.
The role of the knowledge engineer
Knowledge engineers are the people who build the expert system (see Figure
5.17). They are responsible for obtaining information from the human experts and
for designing the structure of the knowledge base and the inference engine. A
knowledge engineer will help experts describe their knowledge and design an
expert system that is attractive and useful. The information presented by the
expert system should be displayed using language that is appropriate to the
intended user of the expert system.
Figure 5.17 A knowledge engineer.
Knowledge engineering is an interactive procedure performed by the knowledge
engineer and the expert to develop an expert system that will solve a problem.
Knowledge engineers need not be experts themselves and should not think that
they are experts. However, a broad experience in the field is a distinct advantage
when the knowledge engineer has to solve a new problem. Knowledge engineers
tend to be verbal, curious and quick to understand complex relationships.
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Storing and retrieving
Storing and retrieving data is a two-step process for retaining data. In DSSs, data
is stored in large databases, such as data warehouses, with intelligent agents used
to search and retrieve data.
Businesses have always relied on unstructured information. The amount of
unstructured information, such as the Internet with Web sites, email and newsgroups, is increasing at a staggering rate. The rapid increase in information has
reached the point where people are being frustrated by information overload.
Decision-makers are facing an increasingly challenging task in searching through
the available sources of information to find the most appropriate ones. Intelligent
agents are tools to help decision-makers.
Intelligent agents
Intelligent agents are pieces of software that search through relational databases
for relevant data. They use neural networks to efficiently search vast amounts of
data. Intelligent agents are independent goal-directed agents that can be launched
into a computer system or network to operate in the background. Intelligent
agents are used in data mining to find relationships and patterns in the data stored
in a database. However, the most common use of these agents is on the Internet,
such as an email agent or a news agent. An email agent can screen a user’s
incoming email for those requiring immediate action. Similarly, a news agent can
be trained to scan articles in a news service and to deliver a personal bulletin based
on the user’s preferences. The main purpose of intelligent agents is to carry out
these tasks faster and more effectively than a human. The hardest thing to
program into these agents is commonsense.
ITITFact
Fact
An intelligent agent is sometimes called a bot (short for robot). They
have been developed to personalise information on a Web site based on
registration information and usage analysis.
Exercise 5.6
1
2
3
4
5
6
7
8
9
10
Explain the difference between primary source and secondary source.
Describe structured data.
What is the meaning of data range?
Describe the role of the expert in an expert system.
What are heuristic rules?
Describe the role of the knowledge engineer.
What is an intelligent agent?
Describe how an intelligent agent works.
List two examples of the use of an intelligent agent.
Outline the main purpose of an intelligent agent.
LEARNING ACTIVITIES
1 The source of data for a particular DSS depends on the particular problem:
a A punter intends to train a neural network program to select winners of horse
races. Suggest sources and types of data that could be included in a training
database.
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Options
b A knowledge engineer is constructing an expert system to assess eligibility for
bank loans. Suggest sources of data for the knowledge base.
c A manager is constructing a spreadsheet model to assist with long-range
planning. Describe some of the primary and secondary sources of data that
might be relevant.
2 There are many popular search engines. Review at least four search engine sites,
including an Australian site, such as webwombat; a meta search engine, such as
dogpile; and a special-interest search engine.
a How are they different? Do they have different rules for using keywords?
b Pick a topic that interests you. Using the same keywords, try your search in the
four search engines. Did you get different results?
c Write a short review of the results of your research.
5.7 Issues related to decision
support systems
Both positive and negative impacts arise in the use of a DSS. In this section, we
examine some of the issues raised by the increasing use of DSS by decisionmakers.
Intelligent systems
Scientists are aiming to give computers the ability to think like humans; this
is called artificial intelligence, or AI. Artificial intelligence is behaviour by a
computer system that, if exhibited by people, would be called intelligent. Artificial
intelligence is used by intelligent systems. Intelligent systems receive data from
the environment, react to that data and produce an intelligent response (see Figure
5.18). They are used in DSSs, such as expert systems, to perform the following
functions.
Figure 5.18 The Sendai railway system in Japan operates without drivers, using
artificial intelligence.
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Preserving expert’s knowledge
Preserving an expert’s knowledge is one of the reasons for developing an expert
system. The factual knowledge supplied by an expert is maintained and applied
even after the expert has changed jobs or moved locations. For example, the
knowledge of specialist doctors can be used to create an expert system. This allows
other doctors without specialist training to access the knowledge of the specialist
doctors. An expert system can also combine the knowledge of many different
experts. Once the expert system has been created, the expert’s knowledge is
stored and available to a range of different users.
It can also be argued that a DSS has resulted in a loss of expert knowledge.
That is, the use of a DSS has resulted in jobs that now require less expertise, such
as tasks involved in authorising, scheduling, pricing and buying. For example, loan
officers have become dependent on the use of a DSS for the approval of a loan.
They do not require the same level of expertise as a loan officer without a DSS.
Improving performance and consistency
DSSs have improved performance and consistency in decision-making. This was
the original reason for creating a DSS. In general, people make decisions in a
limited amount of time based on limited information and with limited processing.
A common problem with decision-making is that the language used to describe
the information influences decision-makers. For example, an 80% chance of
success seems much more positive than a 20% chance of failure. People often give
undue weight to the most recent information, are too confident, or are not prepared to change their opinion. Think about the last decision that you made. Did
you collect all the relevant information and consider all the possible alternatives?
Expert systems will arrive at a decision based on the knowledge of the expert.
These decisions are not objective but are based on the relevant facts of the problem. The decision-making is consistent but not always correct. An expert system
only assists decision-making; it is up to the user to make the final judgement.
Making rapid decisions
DSSs make rapid decisions. They are substantially quicker and more consistent
than an expert in many situations where large amounts of data and numerous
alternatives are to be considered. A DSS provides more information and helps to
generate and define alternatives.
Analysing unstructured situations
DSSs using neural networks and expert systems have improved decision-making
in unstructured areas, such as disaster relief management, mining exploration and
predicting share prices. In an unstructured situation, there is no single method to
reach a decision and no guarantee that the decision will be correct. There are too
many factors or too little knowledge about the situation. DSSs are used to analyse
unstructured situations and provide information to make the situation semistructured. They reduce the problem to obtain a manageable number of
alternative solutions, but they don’t always result in the best solution.
Data mining
Data mining is the process of finding relationships and patterns in the data stored
in a database. It sorts through the data and turns up interesting and often useful
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connections. The information obtained from data mining allows organisations to
make more informed decisions in such areas as improving marketing campaigns
or siting a new store. However, it does raise the issues of erroneous inferences
and privacy.
Erroneous inferences
Data mining identifies patterns in data and infers rules from these patterns. It then
uses additional data to refine the rules based on the original patterns of data.
Erroneous inferences occur when these rules are incorrect. This happens because
many patterns occur by chance, and there is no relationship between the data. For
example, the fact that the sales of ice cream in Sydney are linked to the sales
of socks in Melbourne is a low probability relationship. People need to apply
commonsense when analysing the results from data mining. Decisions made from
data mining must be checked to avoid using an erroneous inference.
Privacy
Privacy is the ability of an individual to control personal data. Personal data used
in data mining is often used in an unintentional way. For example, some businesses
collect and sell information about their customers’ buying habits. Information is
collected at the checkout and combined with a customer profile. The customer
profile is obtained by enticing a customer to use a special card for a discount, such
as earning Frequent Flyer points. This card provides the business with details of
age, sex, income, job and address. Data mining finds relationships between the
customers’ buying habits and their customer profiles. This information is very
valuable for marketing products and providing better services to customers.
However, people’s personal data is being used without their permission. People’s
privacy is being invaded.
The issue of privacy has always existed. However, information technology is
widening the scope of the issue and making the invasion of privacy much easier.
Many common activities leave an electronic trail. Every time a person uses a credit
card or surfs the net, data is added to a database. Data mining is being used to
analyse this data and find relationships. The Internet has countless Web sites that
request information from users. Whenever users fill out a form, they are providing
valuable information. Privacy is invaded when an email from an unknown
organisation is sent to an email address and it uses the receiver’s name. This makes
some people very angry.
The information technology industry is currently self-regulated. There are
many Web sites that provide disclaimers stating that any information provided will
not be used for other purposes. However, these organisations may not have control
of the data in their databases. The federal government has realised that selfregulation is inadequate and is preparing further legislation for privacy protection.
Group decision support systems
Many decisions are made by people in groups. A group decision support system
(GDSS) is an information system that assists users to make a decision by working
together in a group. GDSSs have the potential to improve both the efficiency
and the effectiveness of some kinds of decision-making. A GDSS contains five
main features:
• presentation material—displays information on a screen of previously prepared
material
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• commenting—participants add comments on topics or ideas previously
generated by other participants
• brainstorming—participants add comments anonymously
• voting—participants use the computer to vote on a topic
• evaluation—ranks the alternative decisions based on the preferences of the
participants.
GDSSs are an emerging trend rather
than common practice in business. IBM
has been using GDSSs, and they have
reduced the length of meetings and
allowed people to focus on the particular
topic. The brainstorming feature of a
GDSS encourages participation by
allowing ideas to be entered anonymously.
However, it often increases conflict, as
people are more assertive. For example, a
GDSS makes it possible to tell the boss
that he or she is incorrect without fear of
retribution.
Responsibility for decisions
Research into artificial intelligence led to the development of intelligent DSSs
based on neural networks and expert systems. This provided a class of DSSs that
could replicate an expert’s knowledge and could learn from experience. More and
more tasks are being done by expert systems, including preparing tax returns,
writing wills and diagnosing diseases. However, this increasing dependence on
machine intelligence raises new issues. Who is responsible for these automated
decisions? Do users of these expert systems also require knowledge in the area?
Who would be at fault when a wrong decision is reached as a result of using
a DSS?
There are four participants involved in the development and use of an expert
system: the expert, the knowledge engineer, the professional who uses it, and
the person who is affected by the decision. The problem can be caused by any of
the participants. The expert might have provided inadequate knowledge, the
knowledge engineer might have built the expert system poorly, the user might
have applied the system incorrectly, or the affected person might have supplied
the wrong data. An expert system is only as accurate as the expert and the
knowledge engineer have made it. It will only consider the alternatives thought of
by the expert. It is important to remember that a DSS only provides advice. It is
the responsibility of the user to make the final decision.
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Options
Exercise 5.7
1
2
3
4
5
6
7
8
9
10
11
What is an intelligent system?
Why is it important to preserve an expert’s knowledge?
How can a DSS result in a loss of expert knowledge?
Describe a common problem with decision-making.
How are DSSs used in unstructured situations?
How can erroneous inferences come from data mining?
Describe the issue of privacy in terms of data mining.
What is a GDSS?
Describe the five main features of a GDSS.
List the advantages for IBM of using a GDSS.
Who is responsible for decisions in the use of an expert system?
LEARNING ACTIVITIES
1 The manager of a $100 million pension fund used a neural network instead of
common stockmarket indicators to make investment decisions. When the neural
network suggested that the fund should invest 40% of its assets in bank stocks,
the manager overruled it. In retrospect, the neural network was correct. Explain
why this experience should or should not convince people to overrule a neural
network.
2 ‘The recent advances in technology should make it possible to protect an
individual’s privacy.’ Discuss this statement.
3 Fingerprint analysis is part of the science of biometrics, that is, the statistical
measurement of biological characteristics. Recently biometrics has been used in
fraud detection. Use the Internet to research other applications of biometrics.
Does biometrics have the potential to invade our privacy?
4 You are a passenger on an aeroplane and have just learned that it will be landing
automatically, using an expert system. How would you feel about this situation?
Give reasons for your answer.
5 What are an individual’s privacy rights in New South Wales? (Hint: Visit the Privacy
Commissioner’s Web page.)
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Chapter review
PART A
1 Which of the following is used to
handle uncertainty in a DSS?
A fuzzy logic
B conflict resolution
C data matching
D spreadsheets
2 An inference engine is something that:
A is required in any artificial intelligence application
B produces the rules and inferences
found in an expert system
C acquires the knowledge required to
populate the knowledge base
D is the part of the expert system that
carries out the reasoning
3 Knowledge engineering is:
A the art of designing and building an
expert system
B the process of determining a conclusion from a given set of facts
C the art of designing and building a
neural network
D building a collection of knowledge
4 The three main components of a DSS
are:
A inference engine, model management, explanation mechanism
B data management, model management, dialogue management
C model management, dialogue management, database
D data management, database, user
interface
5 Decision support systems:
A help users make decisions in structured situations
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Options
6
7
8
9
10
B are needed to solve all problems
C need not be interactive
D help users solve problems in semistructured situations
Heuristics:
A are supplied by experts in an expert
system
B are a basis for queries in a relational
database
C are used in spreadsheet models
D are the same as algorithms
An intelligent agent could be used to:
A search expert systems for the right
information
B train neural networks
C filter email
D solve problems
Fingerprint matching as performed by
an AFIS:
A takes days to find a match
B still requires an expert to make the
final decision
C is an incredibly labour-intensive task
D will replace DNA matching
MYCIN is:
A a famous medical neural network
B the first fingerprint-matching expert
system
C a system that can replace doctors
D an aid to diagnosing blood infections
A GDSS is a system that:
A makes decisions for managers
B always uses video-conferencing
C is based on certainty factors and is
interactive
D assists users to make a decision by
working together in a group
Chapter review
PART B
statement number.
Statements
1 A piece of software to search through
relational databases for relevant data.
2 A process of finding relationships and
3 An information system that assist users
to make a decision.
4 Depends on a method to reach a
decision but the correct decision is not
guaranteed.
5 A rectangular grid made up of rows and
columns to organise and store data that
requires some type of calculation.
6 An inference strategy where the user
supplies all the data before the
question is asked or the inference is
made.
7 Starts with one or more possible
solutions and searches back through
the system to determine the questions
to be asked.
8 Provides information and solves problems that would otherwise require a
person experienced in that field.
9 An information system that works like
the human brain and is capable of
learning.
10 A database that collects information
from different data sources.
11 A ready-made expert system except
that it contains no knowledge.
12 An information system that assists users
to make a decision by working together
in a group.
13 A set of general facts and if-then rules
supplied by an expert.
14 Describes the variables that exist between a ‘true’ and a ‘false’.
15 Does not use a method to reach a
decision.
16 An information system that receives
data from the environment, reacts to
that data and produces an intelligent
response.
List of terms
a backward chaining
b data mining
c data warehouse
d DSS
e expert system shell
f forward chaining
g fuzzy logic
h intelligent agent
i intelligent system
j
k
l
m
n
o
p
knowledge base
expert system
GDSS
neural network
semi-structured
situation
spreadsheet
unstructured
situation
PART C
following.
1 Briefly describe four different types of
DSSs.
2 A medical diagnostic DSS can assist a
doctor by providing a patient diagnosis.
It must be able to explain to the doctor
how it reached that diagnosis. Do you
think an expert system or a neural network is suitable for this situation? Give
reasons for your answer.
following terms:
a forward and backward chaining
b structured and unstructured situations
c database of facts and knowledge
base.
4 Describe some of the analysis tools
provided in a spreadsheet.
5 Neural networks have to be ‘trained’.
What does this mean and why is it
necessary?
in DSSs. Identify both the positive and
negative aspects of the issue.
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6
chapter
AUTOMATED
MANUFACTURING
SYSTEMS
Outcomes
Overview
automated manufacturing systems. It investigates specific examples and reasons for
automation. The information processes of an
automated manufacturing system and the social
and ethical issues that relate to these systems
are presented.
6.1 Characteristics of automated
manufacturing systems
Automation refers to the application of automatic control to industrial processes.
It refers to the application of machines to tasks once performed by human beings.
The development of automation has become increasingly dependent on the use of
information technology. This has resulted in automated systems that have become
increasingly sophisticated and complex. Advanced automation systems represent
a level of capability and performance often greater than what people could
achieve. Automation is a term used widely in a manufacturing context.
ITITFact
Fact
The term ‘automation’ was used by D. S. Harder, an engineering manager at
the Ford Motor Company, in 1946. He used the term to describe the
increased use of automatic devices and controls in mechanised production
lines of the automobile industry.
During the Industrial Revolution, products were still custom-made with
manually operated machine tools. The automation concept of the assembly line
became a reality in the twentieth century. It resulted in better and cheaper
goods and services. These automated manufacturing systems out-produced human
workers. Since the 1950s, a great number of scientific and technological
breakthroughs have occurred. One of the most important developments was the
invention of the digital computer. This invention, coupled with the concept of
computer control, has made possible the present-day automated manufacturing
industry.
Manufacturing is the process of producing a product that meets a specific
need. A strong manufacturing industry is necessary for strong economic growth in
the modern world. To maintain a strong manufacturing base, it is necessary to
produce high-quality products from this base. The products must be as cheap as
possible while still maintaining a high level of quality. Automated manufacturing
systems aim to provide these benefits.
An automated manufacturing system is an information system involved in
production by inventory tracking, record-keeping, production scheduling and
actual production. The information technology employed in automated manufacturing systems is divided into several uses. The first use is keeping track of an
inventory and the location of products and parts. The second use is performing the
record-keeping about who did what work, when they did it, and how well they
did it. The third use is related to the actual production, including production
scheduling. Automated manufacturing systems have computerised controls built
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into the manufacturing equipment. Every part of the production is scheduled and
performed automatically. It requires automatic movement of material, precise
scheduling and execution of all work steps, and automatic monitoring of quality
and safety.
An automated manufacturing system has the ability to perform the following
tasks:
• Collecting data from the environment through a wide range of sensors. A
sensor is an input device that measures data from the environment, such as
temperature, pressure, motion, flow and light.
• Processing data into information using a microprocessor as a controller. A
controller receives data from a sensor and changes it into information that can
be used by the system. For example, sensors often collect data in analog form,
and this needs to be converted to digital form for use in the system.
• Performing work on a product. In most cases, the product must be moved from
one location to another during the series of processing steps. At each processing
location, the accurate positioning of the product is generally required. Actuators
perform the actual work of the system, such as stopping a pump, moving a
switch or turning on a light beam. An actuator carries out a mechanical action
under the control of a signal from a controller. Some common actuators are
electric motors, solenoids and stepping motors. (See Figure 6.1.)
Figure 6.1 Automated manufacturing system using robots.
Direct users
Automated manufacturing industries employ a wide range of people with
different skills. Each employee has certain responsibilities in his or her job, and all
employees depend on information and data to perform their jobs satisfactorily.
The organisation of most manufacturing companies is arranged in a hierarchy
of responsibilities. This can help new employees to identify their position in a
company and the people to whom they are responsible (see Figure 6.2). Each
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Options
person employed by the company is dependent on the flow of information
throughout the system. Some people in an automated manufacturing system are
classified as direct users.
(Shareholders)
(Board of Directors)
(Managing Director)
Sales/
Marketing
Technical,
R&D,
Engineering
Casting
Department
Lathe 1
Finance
Manufacturing/
Factory
(Managers)
Procurement
Production
Planning
Production
Quality
Machining
Cell 1
Machining
Cell 2
Finishing
Department
Lathe 2
Grinder
Drill Press
Secretarial
(Managers)
Assembly
Department
(Supervisors)
(Operators)
Figure 6.2 Organisation chart of a manufacturing company.
The direct users are people who interact with or are in control of the
automated manufacturing system. They include both the people using the
machines and the supervisors. The supervisors oversee the operation to ensure that
production does not get behind schedule. Direct users have a task that is
dependent on the information produced during the manufacturing process. The
information in an automated manufacturing system might include the following:
• number of parts needed for a product
• number of employees and skills needed to produce the product
• cost of parts
• cost of production
• sources of component parts
• prediction of market need
• time required to machine or process parts
• number of finished products in stock.
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Block diagrams
A system is a group of elements that work together to achieve a purpose. Systems
are used to understand and explain the world around us. A block diagram is a
diagram used to represent a system. The system is shown inside a rectangle, and
the edge of the rectangle is the system boundary. Circles are used to represent
inputs and outputs that are external to the system. A circle with a line down the
middle is used to represent output from one system that is the input to another
system (see Table 6.1).
Symbol
I
Meaning
External input
System
O
External output
External output/input
Table 6.1 Symbols used in a block diagram.
A system will take one or more inputs and perform a series of actions to
produce one or more outputs. At the simplest level, a block diagram consists of a
single input, a single output and a single system. The block diagram in Figure 6.3
represents the manufacture of a system unit for a personal computer. The input
is the components that make up a personal computer, such as the casing,
motherboard and hard drive. The automated manufacturing system assembles these
parts using a computerised control. The output or product is the system unit.
Computer
Parts
Ι
Assemble
Parts
Figure 6.3 A simple block diagram for the manufacture of a system unit.
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Options
Ο
System
Unit
Refinement is examining a system in greater detail by breaking it down into
smaller parts. Each part is considered a system in itself, or a subsystem. A
subsystem is a small system that is part of a larger system. It also contains a group
of elements that work together to achieve a purpose. The block diagram in Figure
6.4 shows the manufacture of a system unit containing a subsystem for the
motherboard, hard drive and DVD drive.
Casing
Ι
Insert
Motherboard
Insert
Hard Drive
Insert
DVD Drive
Ι
Ι
Ι
Motherboard
Hard Drive
DVD Drive
Ο
System Unit
Figure 6.4 A block diagram for the manufacture of a system unit showing subsystems.
Exercise 6.1
1
2
3
4
5
6
7
8
9
What is automation?
What is an automated manufacturing system?
How is information technology used in an automated manufacturing system?
Describe three tasks performed by automated manufacturing systems.
Explain the difference between a sensor and a controller.
List three common types of actuators.
What are direct users of an automated manufacturing system?
What is the purpose of a block diagram?
List the symbols used in a block diagram.
LEARNING ACTIVITIES
1 Choose a common household product:
a List the raw materials that go into its manufacture.
b List the processes that would go into making this item.
c Draw a block diagram to represent this manufacturing system.
2 Choose an automated manufacturing industry near you:
a Describe this automated manufacturing system.
b Identify the characteristics of this system.
c Draw a block diagram to represent this system.
3 What is the role of accounting in manufacturing? How does an accountant in a
factory depend on using a computer? What sort of information would the
accounting department need in a factory?
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4 What are the different engineering professions that might be employed in an
automated manufacturing industry? Make a list of the jobs that they might do.
5 How is a database used in an automated manufacturing system? Draw a simple
data flow diagram to indicate the flow of data between the customer and the
system.
6.2 Examples of automated
In this section, we examine four examples of automated manufacturing systems
and the reasons for automation.
Specific examples
Four specific examples of automated manufacturing systems are assembly line
production, automated warehouses, CAD/CAM and mail sorting.
Assembly line production
Assembly line production is a series of workstations connected by a transfer system
that moves parts between each workstation. Each workstation is designed to
perform a specific processing operation, so that the product is gradually constructed
as it progresses along the line. Raw materials enter at one end of the line, proceed
through each workstation, and emerge at the other end as a completed product.
Workstations are simultaneously processing a part of the product. One finished
product is produced with each cycle of the line. Assembly line production requires
various operations and product transfers to be properly coordinated. This is
controlled by special computers called programmable logic controllers. PLCs are
the main process control computers used in manufacturing. They are used for data
capture and actuator control and to perform timing and sequencing functions.
Assembly line production is
applied in many industries, such as
the car industry (see Figure 6.5).
A typical car has over 5000
separate parts that need to be
assembled to produce the final car.
A large car manufacturer, such as
Mitsubishi or Ford, might employ
3000 to 4000 employees in such
jobs as accounting, management,
car assembly, warehousing and
marketing. Car assembly often
requires some products from other
manufacturers. An example would
be the alternator and electrical
systems used in a car. The car
manufacturer needs to keep a
database on the quantity and stock
number of each part so that
reordering from the warehouse is
Figure 6.5 Assembly line production.
not a problem. On the assembly
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line, information needs to be kept about production times, machine maintenance,
faults in production and total number of cars produced over a set period. Cars
need to be labelled and packed for various destinations both interstate and
internationally. Assembly line production is very important in the car industry for
maintaining good quality control, as well as for reducing the cost of production.
ITITFact
Fact
Automation was seen to be a valuable asset in the early 1930s when Henry
Ford produced his famous Model T car.
Automated warehouses
An automated warehouse uses automatic control for the storage of products (see
Figure 6.6). It is a very important aspect of modern businesses. Manufacturing
industries need to be able to store parts that are used to make up a final product,
as well as to store products for future customer orders. The tracking of warehouse
items is necessary for the following reasons:
• knowing when to reorder a part
• monitoring the daily or weekly use of a part
• knowing which products are not being sold
• calculating capital tied up in warehouse stock
• being able to assemble customer orders from warehouse stock
• knowing what space is available for new product storage.
The above reasons have been
influential in the progress and development of automated warehouses.
Automation has taken the form of
automatic tracking by using barcodes
on the products or parts in the
warehouse. By scanning an item’s
barcode and storing this information
in a database, it is possible to know
everything about the product or part,
as well as its storage location in the
warehouse. Automated warehouses
use machines independent of human
guidance for loading or unloading a
product. These machines are controlled by a central computer linked
to the database. This computer
system is used to track products across Figure 6.6 Jobs such as this may become redundant as
multiple warehouses that may be warehouses become increasingly automated.
separated from each other by large
distances.
CAD/CAM
CAD (computer-aided design) is the use of information technology to design and
analyse a product or object. Designers working with a CAD system, rather than on
a traditional drafting board, create the lines and surfaces that form the object and
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store this model in the database. The CAD software allows the designer to
perform various analyses on the object, such as heat transfer calculations. The
design is refined by adjustments made on the basis of these analyses. Once the
design procedure has been completed, the CAD system generates the detailed
drawings required to make the product.
CAM (computer-aided manufacturing) refers to the specialised information
technology tools that automate the entire manufacturing process. A computer
system is used to automatically control the actions of the plant equipment. It is
also used to monitor the collection of data from the factory, the analysis of the
data, and the communication of results to management.
A CAD/CAM system involves not only the automation of the manufacturing
operations but also the automation of elements in the entire design and
manufacturing procedure. The combination of CAD and CAM has been applied
in many industries, such as machined components, electronics products and
equipment design. CAD/CAM systems often use numerical control machines.
Numerical control (NC) is a form of programmable automation in which
numbers control a machine. The initial application of numerical control was in the
machine tool industry. It was used to control the position of a cutting tool relative
to the product part being machined. The numbers are coordinates in three
dimensions that define the exact position of the cutting tool in relation to the
product part. It then uses a program to sequence the coordinates that direct the
cutting tool to machine the part. NC usually receives feedback from the system to
ensure the program has been correctly performed.
NC technology allows complex parts to be fabricated quickly and accurately
by automated machine tools that directly drill, grind, cut, punch and mill to turn
raw material into a finished product. NC machine tools use a numerical control
method for activating the tools in response to a predetermined command stored
as digital data on tapes or in semiconductor memory. The programs have two
functions: positioning the tool point in three dimensions relative to a product part
and controlling secondary functions, such as speed, feeding, coolant flow, gauging
and tool selection.
There are basically three types of NC machine tools. The first is the conventional NC system where functions are wired together in a fixed pre-engineered
arrangement. The second is computer numerical control (CNC) in which a
microprocessor is programmed to control some or all of the NC functions. The
third approach is direct numerical control (DNC) in which a group of NC (or
CNC) machine tools are simultaneously controlled by a host computer.
Many applications of NC have been developed since its initial use to control
machine tools. NC is used in electronic assembly, drafting machines that prepare
engineering drawings, coordinate measuring machines that perform accurate
inspections of parts, and flame cutting machines. In all these applications, coded
numerical data is employed to control the position of a tool or workhead relative
to some object. The four advantages of NC machine tools over standard machine
tools are:
• one person can operate more than two NC machine tools
• greater accuracy with better repeatability
• the ability to process products that have complex shapes
• shorter processing time.
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Mail sorting
Mail sorting involves the collection, sorting and delivery of mail to various homes
and businesses. In the early days of postal sorting and delivery, people sorted the
mail by hand, reading the addresses and sorting the mail into groups based on
cities and towns. Once sorted into various destinations, the mail was then
transported to the city or town and then re-sorted to a final level for delivery to
the home or business. Mail sorting became easier with the advent of postcodes and
machine-stamped codes on envelopes. Today, automated mail sorting machines
accept a wide variety of letters and parcels and have the ability to sort them
quickly and efficiently. Automated mail sorting machines use optical character
reader (OCR) machines.
An example of an OCR machine is the Electrovision EV-40. The EV-40 is used
in high-volume outbound and incoming mail applications. The EV-40 is entirely
software based. If the EV-40 is installed in an automated mail-sorting machine, it
scans 10 cm vertically, starting at the bottom of the mail piece, and 28 cm
horizontally. It optically reads and interprets four lines of the address block on
machine-printed mail. This information is converted to a barcode, and the
envelope is encoded with this barcode. This means that high-volume mailers
achieve higher percentages of barcode mail, which leads to greater cost savings
and higher efficiency in mail operations.
The National Presort Inc NP-8000 is a machine that can sort up to 40 000
mail pieces per hour and handle small flat parcels as well. This machine allows
a computer to monitor mail and check for changed addresses, as well as other
accounting information, that can be used by various businesses.
Reasons for automation
Automated manufacturing systems are able to repeat their actions accurately. For
the automobile industry, this means that quality control is maintained on all cars
by the use of machines that do not tire on the production line. It is possible to run
machines for many hours at little cost, and this reduces costs associated with car
manufacture. This reduction in cost by the use of computer-controlled machines
also applies to other industries. The
ability of machines to run for long
periods of time on repetitive tasks at a
reduced cost also means productivity
gains.
When designing new products or
modifying older products, computers
can be used to help automate the
design process. The software used in
CAD allows the user to make a virtual
model in the computer. This modelling
can be used to simulate the sizes that a
product may need to have or perhaps
the wear and tear that might occur in a
certain situation. A simple example
might be the design of a seat in a car.
The computer can automatically, with
the help of an engineer, design a seat
that can then be simulated to see if it
will fit neatly into the car. It can also be
tested for proper movement for
different sized people. If the design is
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found to be unsatisfactory, then it is relatively easy to modify the design using the
CAD package. This leads to design gains through simulation and modelling.
Another major advantage of automation is increased safety. Automated manufacturing systems can protect people who must work in high-risk working
environments, such as welding car doors or operating a dangerous machine.
Sensors can collect data about the operator’s position, as well as information about
the machinery and raw materials. A simple example would be a sensor detecting
that an operator’s hand is too close to a revolving shaft and automatically stopping
the shaft, as well as signalling an alert on a display device. This information can
also be logged into a central database for later evaluation of safety features and
their effectiveness. The information could also be used for aggregate safety
statistics on the machine floor.
Case study
Arco Saucepans
Arco is a company that manufactures saucepans. The saucepans are made from plate
steel in a factory. The design of the saucepan is done with the help of a CAD system.
It stores the three-dimensional design of the
saucepan along with the relevant sizes of
sides, bases and lids; base thicknesses; and
hole positions for the handles in a CAD
database. The weight of each saucepan
is automatically calculated by the CAD
package. This information is made available
to a DBMS. Data is required by:
• finance employees to estimate the cost
for each saucepan and the necessary
mark-up of the product
• marketing employees to describe the
size of the saucepan, as well as its
colour and handle shape if it has a
choice of handle shapes
• pressing machine operators on the
factory floor to provide the thickness of
material to be pressed by the machine
into the saucepan so that the sizes and
tolerances can be set on the machine
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• quality control employees to ensure
that the handles are fixed on properly
and will not shake loose, as well as to
ensure that the saucepan base is flat
and won’t wobble on a stove
• customers (retailers) to know what
materials the saucepan is made from
and its life expectancy, as well as the
price.
The flow of data in this automated
manufacturing system is important. It is
used in different ways by different people
and is obtained from a central database.
The information is collected from different
points in the factory, including the design,
finance, marketing and quality control
units. On the shop floor, the data is
collected using a range of sensors and
transferred to the database. The sensor
data from the production line is also used
to control actuators that will start motors
and other machinery to manufacture the
saucepan.
Exercise 6.2
1
2
3
4
5
6
7
8
9
10
11
12
Describe an assembly line production.
What is performed by PLCs?
How is assembly line production applied in the car industry?
What is an automated warehouse?
Explain the difference between CAD and CAM.
What is numerical control?
List the three types of NC machine tools.
Outline four advantages of NC machine tools over standard machine tools.
Why are automated mail-sorting machines used?
List some of the reasons for automation.
How does automation achieve increased safety?
The following questions relate to the Arco Saucepans case study:
a What is stored by the CAD system?
b List the people who require data from the database.
c Describe the flow of data in this automated manufacturing system.
LEARNING ACTIVITIES
1 Automated manufacturing systems perform information processes requiring
participants, data/information and information technology for the following
automated manufacturing systems:
a assembly line production
b automated warehouse
c CAD/CAM
d mail sorting.
2 Discuss the relationships between participants, data/information and information
technology for the following automated manufacturing systems:
c CAD/CAM
d mail sorting.
3 Outline the reasons for automation in each of the following automated manufacturing systems:
c CAD/CAM
d mail sorting.
4 What cars are assembled in Australia? Are all the parts made in Australia? Identify
ten parts that go into building a car. Briefly outline the advantages and disadvantages of the same company manufacturing every part of a car rather than
buying parts from other manufacturers.
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6.3 Collecting in automated
Collecting for an automated manufacturing system involves using CAD/CAM,
sensors, barcode readers and analog-to-digital conversion.
CAD/CAM
CAD/CAM is the use of computers to perform many of the functions related to
design and production. It is based on the ability of a computer system to process,
store, and display large amounts of data representing both part and product
specifications. CAD refers to the use of information technology to design and
analyse a product. CAM refers to the specialised information technology tools that
automate the entire manufacturing process. The CAD/CAM system can be
regarded as a flow of information from the design workstation to the database and
then from the database to the factory machinery (see Figure 6.7).
CAM
CAD
Numerical Control
Geometric Modeling
Robotics
Analysis
Data
Base
SPE
CS
Interactive
Terminal
Process Planning
Product Specifications
Automated Drafting
Automated
Factory
Factory Management
Figure 6.7 CAD/CAM relationship through a common database.
A CAD system requires a high-performance computer with specialised CAD
software and a plotter. The CAD software is made up of different software
modules that carry out specific tasks, such as circuit analysis or three-dimensional
solid modelling. The CAD software stores the designs and provides data for a
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database. This data consists of product specifications, such as plate thickness,
number of screws needed, size of sheet metal base, weight of product and overall
dimensions for packaging. The information from the CAD system stored in the
database is used by the CAM system. Some of the commonly available functions
provided by CAD software are:
• image manipulation—add, delete and edit images
• transformations—rotate, translate and scale images
• libraries—store standard and customised drafting symbols
• file management—create, merge and delete image files.
Automated manufacturing systems use the data supplied by a
CAD/CAM system for other functions in the organisation. A CIM
(computer-integrated manufacturing) system includes all the engineering functions of CAD/CAM
plus the business functions of the
organisation. The business functions include order entry, cost
accounting, employee payroll and
customer invoicing. CIM involves
computerised data collection and
integrated flow of data between
design, manufacturing and planning. It applies information technology to all the operational and
information processing functions.
CIM has benefited by recent technical advances, such as increased
Figure 6.8 Computer-integrated manufacturing.
computer power, better data management and faster communications. CIM represents the highest level of automation in manufacturing.
Sensors
Sensors are input devices that measure data from the environment. They convert
input provided by the environment into a signal that can be communicated to a
control program. Recent advances in technology have provided a vast array of
sensors, such as highly sensitive electromechanical probes, scanning laser beams
and machine vision. Machine vision, which requires the processing of large
amounts of data, can be accomplished only by high-speed computers. It is being
used for many manufacturing tasks, such as part identification, quality inspection
and robot guidance.
Sensors are sometimes referred to as transducers because they convert one
physical quantity into another. They often generate a potential difference, or
voltage. For example, a tachometer is a rotational speed sensor that converts
velocity into a voltage. A good sensor needs to rate highly on the following criteria:
• accuracy—the difference, if any, between the value of the measured variable
and the measurement obtained by the sensor
• resolution—the level of change to which the sensor will respond by changing
its output
199
• repeatability—the variation, if any, shown by the sensor over repeated
measurements of a given value
• range—the upper and lower limits of the sensor’s measurements
• dynamic response—the maximum frequency of change in a measured variable.
ITITFact
Fact
Sensors are used by robots to inspect the manufacturing process. They determine whether each machine part is consistent with quality specifications.
Sensors are used to detect different physical conditions, such as temperature,
pressure, motion, flow and light.
Temperature
Temperature sensors are devices that measure the temperature of the air, a fluid
or an object. The control of temperature is very important in many industries.
Different temperature sensors are required for different applications. Some
sensors would be inappropriate due to the range of temperatures they detect, their
sensitivity or their fragility. Temperature is detected using the resistance of a
conductor. When the temperature rises or falls, the resistance of the conductor
increases or decreases. The three main types of temperature detectors are the
resistance thermometer, the thermocouple and the thermistor.
• Resistance thermometers measure temperature using a metallic conductor,
such as copper, nickel or platinum. The conductor’s resistance to electrical
current increases with temperature. The metal is either wound as a coil or
deposited as a thin film onto some suitable material called a substrate.
Resistance thermometers are available for temperatures that range from 200°C
to 800°C.
• Thermocouples measure temperature using two different metals (a couple) in
electrical contact. A voltage is produced that is proportional to their temperature difference. The point at which the two different metals meet is called
a thermojunction. The thermocouple has two such junctions: one held at a
reference temperature and the other in contact with the temperature source
that needs to be measured. A temperature difference has to be provided to
make a thermocouple work. The temperature range for thermocouples is quite
large, being from 250°C to 1400°C.
• A thermistor (thermal resistor) is a semiconductor device that measures temperature in a manner similar to a resistance thermometer. The resistance of the
semiconductor in a thermistor is very rapid. This makes thermistors more
sensitive than resistance thermometers to small changes in temperature.
Pressure
Pressure sensors are devices that measure the exertion of a force. Pressure in a
pipe or container can be sensed by using a pressure gauge. The gauge is designed
in such a way that the liquid or gas that is being measured is connected to a curved
tube. The higher the pressure, the more the tube is forced into a straight line from
its initial curved position. The amount of movement is turned into a voltage by
using a variable resistor called a potentiometer. This resistor has an electric current
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passing through it, and the difference in voltage can be detected as the resistance
changes. This voltage is then used to register the pressure. The same effect can be
obtained by using a diaphragm.
A diaphragm is usually a small circular piece of material held inside a small
container with one surface in contact with the liquid or gas being measured and
the other exposed to normal air pressure. A diaphragm is made of flexible material
that will move different amounts according to the pressure on one side of the
diaphragm. This movement is converted into a voltage in a manner similar to
the one mentioned above. In some diaphragm devices, the diaphragm is directly
connected to a piezoelectric material, and the voltage is generated by the pressure
being applied to the material. This voltage is then passed as a signal back to the
computer.
Motion
Motion sensors, or velocity sensors, are devices that measure the rate of change of
position. They calculate how far an object has moved from a starting position.
They use electromagnetic induction to produce a voltage proportional to the
velocity of a conductor (wire) moving in a magnetic field. The device consists of
an armature with fixed magnets around it like an electric motor. Rotation of the
armature produces an induced current in the windings and a voltage proportional
to the rate at which the conductor is being rotated.
Acceleration sensors depend on the piezoelectric properties of materials, such
as quartz or ceramic crystals. A crystal is attached to the base of a mass. As a force
is applied to the crystal and then onto the mass, a small electric current is
generated in the crystal due to the strains that are set up.
Flow
Flow sensors are devices that detect the motion of fluids, including liquids and
gases. They are often used to measure the flow of liquids and gases through pipes
and drains. One method of detecting a flow of liquid is to have the liquid turn a
small paddle wheel just like an old water wheel. The speed with which the wheel
turns gives a measure of the flow of the liquid. The wheel is attached to a
tachometer, and the voltage generated by the tachometer is proportional to the
flow of liquid. Another type of flow sensor uses an ultrasonic signal to detect the
change in frequency of the returned signal due to the interference of the passing
liquid or gas. The change in frequency is converted to a voltage or current
proportional to the flow of liquid or gas.
Light
Light sensors, or optical sensors, are devices that can detect changes in the level of
light. They are used in industrial processes to detect imperfections in products. For
example, in steel milling, light sensors detect irregularities in the rolled steel as it
passes along the rolling mills. Light sensors are used to control the motion of
robots and their interpretation of the environment. Researchers are working very
hard at interpretation of light images received by various detectors. The two main
problems associated with light sensors on robots are:
• High bandwidth. The large amount of data to be transferred requires very high
frequencies. The higher the frequency of the bandwidth, the more bits per
second that can be transmitted.
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• Enormous amount of processing. Each piece of data or pixel contained in the
picture requires calculations to determine whether it is part of an object.
These problems do not arise in simple optical devices used for brightness
detection. These devices may only detect differences between black and white,
such as the dark lines and white spaces in barcodes. The development of solidstate optical sensor arrays has reduced both costs and processing requirements. An
example of these light sensors is a photodiode.
A photodiode produces a voltage in proportion to the amount of light falling
on its surface. The most common use of photodiodes is as a light-beam switch. A
source of light is placed to strike the diode; and if the beam is interrupted, the
voltage of the diode falls. This device can be used for many applications that need
to detect when an object is present or not present. A simple example would be
the detection of customers walking into a shop. In an automated manufacturing
situation, the computer might wait for a break in the light beam to signal that a
part has moved onto a conveyor belt or near a robot. The computer would then
send a signal to the robot or to another machine to cause some action to happen.
Images from the outside world can be detected by the use of a two-dimensional
array of solid-state devices called charge-coupled devices (CCD). A twodimensional CCD is made up of a grid of photosensitive elements. The more light
at each location in the grid, the more electrical charge. CCD devices are made into
very robust and accurate cameras for use on robots and in industry. CCD cameras:
• work at low voltages and have only a small power requirement
• are very accurate at positioning objects
• are not damaged by intense light
• are sensitive over a wide spectral range (light range)
• do not have memory and so moving objects are not smeared.
Barcode readers and inventory tracking
Figure 6.9 Barcode reader.
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Barcode readers are input devices that allow a
computer to read barcodes found on products
or parts (see Figure 6.9). The barcodes contain
information about the product or part. This
information is needed by managers to track
how many products are available to sell and
how many parts are available for use in manufacturing the products. The total number of
products or parts held is called an inventory.
This information is vital if the factory is not to
run out of components that go into the finished
product and thus delay production. It also helps
the managers determine how quickly products
are selling and whether a suf-ficient quantity
has been scheduled for manufacturing. The
majority of companies label parts and products
with barcodes. The use of barcodes enables easy
tracking of the parts through the factory as well
as easy warehousing of parts and products.
A barcode is represented by a pattern of wide
and narrow bars. The barcode reader scans the
bars and translates the different patterns back
into regular characters and sends them on to a
computer for further processing and storage. The processing might involve
calculating the cost of an item, as in supermarkets, or making a decision about
the item, such as whether to machine it or stack it in box.
ITITFact
Fact
Barcodes were first developed for U.S railways to keep track of which
carriages went with which engine. The barcodes were imprinted at a
uniform height above the ground on the side of railway carriages that went
with a particular ‘system’. The barcodes of the different carriages could then
be read to compile information on particular groupings of carriages.
Every barcode starts with a special start character and ends with a special stop
character. These codes help the barcode reader detect whether to start scanning
forward or backwards. Some barcodes may include a checksum character just
before the stop character. When the barcode is printed, a checksum is calculated
from the characters in the barcode. The barcode reader performs the same
calculation and compares its answer to the checksum it read at the end of the
barcode. If the two numbers don’t agree, then the barcode reader will try to read
the barcode again.
There are different barcodes, each with its own particular pattern of bars. For
example, the UPC-A code is used in retail in the USA, has twelve numeric digits,
and identifies the manufacturer and particular product. Other codes, such as
Code39 and Code128, include upper-case and lower-case letters, digits and a few
symbols. EAN-13 is the code used in Australia, as well as other countries, for
marking retail goods. It consists of thirteen digits: the first two or three are a
country code, followed by nine or ten digits and a single-digit checksum.
Supplementary two-digit and five-digit barcodes are sometimes added to the
code. Each participating country has EAN barcoding authorities that regulate
the use of retail barcodes.
The last digit in the EAN barcode is a checksum and is a modulo-10
calculation. The algorithm to calculate the checksum is given below:
1 Add the values of the digits in the even positions (positions 2, 4, 6 etc.).
2 Multiply this result by 3.
3 Add the value of the digits in the odd numbered positions (positions 1, 3, 5
etc.).
4 Sum the results of steps 2 and 3.
5 The check digit is the smallest number that, when added to the result in step
4, produces a multiple of 10.
1
2
3
4
5
For example, to find the checksum for the barcode 012345768901:
1+3+5+6+9+1 = 25 (adding the digits in the even positions).
25×3 = 75 (multiplying the result by 3).
0+2+4+7+8+0 = 21 (adding the digits in the odd positions).
75+21 = 96 (adding the results of steps 2 and 3).
96+x = 100 (finding the smallest number that, added to the result in step 4,
will produce the nearest multiple of 10).
Therefore, the check sum is 4 (96+4 = 100).
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Analog-to-digital conversion
Data collected from sensors is often in analog form, and this needs to be converted
into digital form so it can be used by a digital computer. A device used to change
analog into digital is called an analog-to-digital converter (ADC). Data may also
need to be converted from digital back to analog. A digital-to-analog converter
(DAC) is a device that converts a digital signal into an analog signal. Most ADCs
are also DACs.
An ADC takes an analog signal, such as a voltage or electric current, and
electronically converts it into digital data. The digital data comprises a number of
bits, such as eight, sixteen, thirty-two or sixty-four. The more bits that are used,
the more expensive the ADC. For example, a temperature sensor might measure
a range of temperatures from 0°C to 100°C using a voltage range from 0 to 5 volts.
If the temperature is 40°C, a voltage of 2 volts will be produced. The computer
stores its data in a byte made up of eight bits, and a range of values from 0
(00000000) to 250 (11111010) can be used. The ADC must change a voltage
range of 0 to 5 into a value range of 0 to 250. The mathematics required involves
dividing the voltages by 5 and multiplying the result by 250 (see Table 6.2).
A reading of 2 volts from the temperature sensor is converted to a decimal
number of 100 or a binary number of 01100100 inside the computer. It is
important to note that the temperature is only measured to the nearest 0.4°C
since digital devices are restricted to discrete quantities, in this case 0 to 250. For
example, 1°C would be represented by 0.05 volts, but this voltage converts to 2.5
and cannot be represented as a discrete quantity on a digital scale of 0 to 250.
Temperature (°C)
Volts
Decimal
Binary
0
0
0
00000000
0.4
0.02
1
00000001
0.8
0.04
2
00000010
1.2
0.06
3
00000011
1.6
0.08
4
00000100
2.0
0.10
5
00000101
:
:
:
:
19.6
0.98
49
00110001
20
1.00
50
00110010
40
2.00
100
01100100
60
3.00
150
10010110
80
4.00
200
11001000
:
:
:
:
99.6
4.98
249
11111001
100
5
250
11111010
Table 6.2 Analog-to-digital conversion for the example temperature sensor.
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Damping
Damping is a decrease caused in the amplitude of successive oscillations or
waves. For example, shock absorbers in a car are a damping device. They restrain
the motion of the car’s springs so that the expansion and contraction of the springs
do not shake the car excessively. When applied to automated manufacturing
systems, damping is the process that modifies the signal to the output device
based on the input signal. Signals are received from a sensor, the controller changes
these signals into information, and the actuator carries out some action. The rate
at which a system responds to the controller is very important, and damping
devices help to determine that response rate. There are three types of damping
(see Figure 6.10):
• Overdamping occurs if the change is too slow, and the actuator takes longer to
reach the desired level or position. However, overdamping does not overshoot
the desired level. It is a slow reaction to change and return to stability.
• Underdamping occurs if the change is too fast, and the actuator overshoots the
desired level. Underdamping then causes a return movement that will also be
too quick, causing the actuator to undershoot the desired level. Underdamping
is a quick reaction to change resulting in rapid fluctuations before stability is
reached.
• Critical damping is the preferred rate of change in the output of the system.
The desired level is achieved in the quickest amount of time. Critical damping
is a quick reaction and a quick return to stability.
Final
Measured
quantity
Initial
Critical damping
Time
Final
Measured
quantity
Initial
Overdamping
Time
Final
Measured
quantity
Initial
Underdamping
Time
Figure 6.10 Damping.
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Exercise 6.3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Describe a CAD/CAM system.
List some of the functions commonly provided by CAD software.
Describe CIM.
What is a sensor?
Describe the three main types of temperature sensors.
How does a pressure gauge work?
What is calculated by motion sensors?
Describe the two main problems associated with light sensors on robots.
What is a photodiode?
Describe the use of barcodes in a factory.
Calculate the checksum for the barcode 108976453811.
What does an ADC do?
What is damping?
Which type of damping is the preferred rate of change?
LEARNING ACTIVITIES
1 Aeroplanes are fitted with an automatic cruise control that keeps the plane at a
steady speed.
a Draw a block diagram of this system showing the flow of data within the system
and the sensors required.
b Describe the operation of one sensor that would be needed in the cruise control
system.
c Describe the effect of underdamping in this system.
2 Collect some barcodes from various objects. What do you notice about the first
character? The second character? If the barcode has 13 characters, check the
checksum using the algorithm presented in the text.
3 Pick two examples where damping can be seen. Describe for each example what
the effect of overdamping, underdamping, and critical damping would be.
4 A sensor measures temperatures from –20°C to 30°C using voltages ranging from
0 to 5 volts. Convert the following temperatures into bytes (range from 0 to 250)
that the computer can understand:
a 30°C
b –10°C
c 0°C
d 20°C
5 Suppose you had to get a computer to make a measurement of a voltage that
ranged from 0 volt to 200 volts. Assume that the ADC used 8 bits to encode the
range, using a value range of 0 to 250.
a What would the digital 8-bit reading for 160 volts be?
b What would the digital 8-bit reading for 100 volts be?
c What would the digital 8-bit reading for 20 volts be?
d How accurately could the computer read a voltage?
e How would the accuracy increase with a 16-bit ADC?
6 Use a CAD software package to design a personal computer.
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All information processes play a role in automated manufacturing systems,
including processing, displaying, and transmitting and receiving.
Processing
Processing data for an automated manufacturing system is the manipulation of the
data. After the data is collected, it must be converted into a form for transmission.
This process involves mass production and types of production.
Mass production
Mass production is the manufacture of products in large quantities by standardised mechanical processes. It is based on four basic principles:
• Production is divided into specialised tasks that are relatively simple and highly
repetitive.
• Standardisation of parts, such as dimensional tolerances, allows parts to be
readily fitted to other parts without adjustment.
• Specialised machines, materials and processes minimise the amount of human
effort and maximise the output.
• Systematic planning of the total production process permits the best balance
between human effort and machinery.
The principles of mass production have led to lower costs and major improvements in uniformity and quality. Large volumes and standardisation have allowed
statistical control and inspection techniques to monitor production and control
quality. Mass production is used to manufacture a range of products, such as
cars, televisions, refrigerators and kitchenware. Individual parts of these products,
such as batteries and refrigerator compressors, may also be mass-produced. The
workforce in mass production is usually semi-skilled for machine operation and
assembly. Industrial robots are used in many mass production industries.
Inflexibility is a major problem of mass production. Maximum efficiency is
achieved by using specialised tools, standardised parts and a very structured
process. Redesigning a product is expensive, as the new design may make the old
tools and machinery obsolete. Organisations are now using machinery with builtin flexibility. For relatively little extra cost, the tooling can be changed to adapt
the machine to accommodate changes in design. In addition to allowing greater
flexibility, this machinery provides opportunities to make customised products.
There is a trend towards customising a product to meet the needs of individuals.
It is an attempt to retain the advantages of mass production while providing
customised value. The manufacturer regards the product as mass-produced, while
the customer regards the product as customised.
ITITFact
Fact
Early cars were mass-produced with every unit identical to every other unit
in all aspects, including their colour, which was black.
207
Types of production
The three types of production used in automated manufacturing systems are
continuous, batch and discrete.
Continuous systems are capable of operating 24 hours per day for weeks or
months without stopping. Specific times are set aside for maintenance and finetuning of the manufacturing system. The manufacturing equipment used for a
continuous system is specially designed for the individual industry and its product.
The product being made is often required in bulk form with the output measured
by volume or weight. Continuous systems are often used in chemical manufacture, food production and the processing of certain basic metals. In these
operations, the products are processed in gas, liquid, or powder form to allow the
flow of the material through the various steps of the production cycle.
A batch system is a discontinuous system that produces a specific quantity of
a product. The quantity of the product is called a batch run, or production run.
Batch runs may produce several dozen to thousands of units of a product. A batch
run may have to be repeated at a later time. Batch systems are used to manufacture different types of products using the same manufacturing equipment.
Consequently, the manufacturing equipment in a batch system must be much
more flexible than that in a continuous system. To provide flexibility, workers in
a batch system will need to be more highly skilled than workers in a continuous
system. Metals are typically produced in batches rather than continuously as it is
generally more difficult to handle metals in bulk form.
For each new batch, the manufacturing equipment must be reprogrammed and
changed over to accommodate the new product. The time required for this
changeover is a disadvantage of batch systems. It is lost production time. However,
the variety of products in batch systems is limited, and the changeover of
equipment can be done very quickly. In a large batch manufacturing system, there
are often control and scheduling problems because batch runs are needed for
different products, with different customers and at different delivery times. Batch
systems require a coordinated approach to material ordering, warehousing and
part machining. Information systems can be a useful tool for solving these
problems. Batch systems are used to make such products as spare parts for aircraft,
cars, trucks and construction equipment.
A discrete system is a discontinuous system that performs a single task in a
small time interval. It produces items made to a customer’s exact specification and
is sometimes called ‘jobbing’. Discrete systems use general-purpose machines,
such as lathes and hand tools. The workforce is more highly skilled to make very
specific products. Discrete systems manufacture products with the highest unit
cost. Examples of products made with discrete systems include space satellites,
ships, oil rigs and special-purpose manufacturing equipment.
Products are often made using a combination of continuous, batch and discrete
systems. For example, a large ship is the only one of its kind, and this implies a
discrete system. However, the steel plates in the hull are produced by continuous
casting and rolling in a steel mill. They are made using a batch system.
Displaying
Automated manufacturing systems display information by performing some
work on the product. They use specialised display devices called actuators and
may have to convert data from digital to analog so that the actuators can perform
their tasks.
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Actuators
An actuator is a display device that performs a mechanical action under the
control of a signal from a controller. Actuators perform the actual work of the
system. Some common actuators are solenoids, electric motors, stepping motors,
relays and hydraulic pumps.
ITITFact
Fact
A ‘cell’ is an autonomous manufacturing unit that can produce a finished
product. Control at the cell level involves scheduling of individual parts
onto machines.
A solenoid is a coil of wire around a movable magnet (see Figure 6.11). When an
electric current passes through the wire, a magnetic field is generated that will move
the magnet in the centre of the wire coil in one direction or the other depending on
which direction the current is going. Washing machines use a solenoid to control the
level of water entering the tub. The solenoid is attached to a small valve, which can
be opened or closed depending on the electric current in the solenoid.
Degree of
movement
On/off electric
current
Solenoid coil
Iron rod core
Figure 6.11 Solenoid.
Electric motors are clean and capable of high precision if operated carefully.
Electric direct-current (DC) motors are very popular actuators because of their
ease of use. DC motors run continuously, first in one direction and then in the
other direction. The motion remains smooth and continuous. There is no
particular inherent control of position in DC motors. DC motors develop large
torques. Torque is the shaft-turning power that a motor can output. A high torque
means that the shaft can move a load easily. An example of a high torque value
used in an antisocial way is the spinning of car wheels at traffic lights. A DC motor
can have its direction changed by reversing the current in its electric windings.
This can be done by a relay or by power amplifiers electronically switching the
direction of current flow. DC motors are capable of high precision, fast
acceleration and high reliability, making them good candidates for converting an
incoming signal into mechanical motion.
Stepper motors are used in robots when precise open-loop control is needed.
Open-loop control means that the desired position is calculated and then the
device, or system, is told to go to that position. A stepper motor allows this to
happen easily. It is capable of being told to rotate through a number of degrees
and then stop. It can rotate in either direction, just as a DC motor can, but it stops
209
after a very accurate number of degrees. For example, a stepper motor can be
instructed to rotate exactly 20 degrees to the right and then 120 degrees to the
left. A disadvantage of the stepper motor is that it has a low torque compared with
a DC motor and usually takes up more space than a DC motor. This means that,
if a robotic device needs to move heavy loads, a stepper motor is not a good
choice. Another disadvantage is that stepper motors accelerate and decelerate at
each step and therefore do not provide a smooth and continuous motion.
A relay is a switching device. It is primarily used when a small electric current
is used to turn on or turn off a large electric current. The device is made from a
solenoid in which the movable magnet is connected to a mechanical switch, which
is held in a default position by a spring. When an electric current passes through
the coil, the magnet moves against the spring and causes the switch to either open
or close. The switch is usually connected to a more powerful electric source than
the activation current for the coil. This means that a small voltage can control a
much larger current or voltage switch. This also means that the signal currents can
be isolated from a much more dangerous current grid. Sometimes many different
switches may be connected to the moving magnet in the coil, and this allows one
relay to control many motors or other electric devices.
Hydraulic pumps are used when great strength is needed. A hydraulic fluid
powers the pump, or actuator. Hydraulic fluids are non-compressible fluids, such
as oil, that can be used in very high-pressure situations. The power transmitted by
the hydraulic fluid comes from the pressure the fluid exerts against things and not
from compression of the fluid itself. The power from a hydraulic pump is
transmitted through high-pressure tubing to a hydraulic device and then returned
to the fluid supply tank.
Digital-to-analog conversion
Displaying data may require converting digital data from the computer system
into analog data for an output device. A digital-to-analog converter (DAC) is a
device that converts a digital signal into an analog signal. For example, the
computer might be connected to an actuator, such as an electric motor. This
electric motor might be designed to accept voltages ranging from 0 to 10 volts.
Therefore, the DAC could convert the digital signals in the range 0 to 250 into
voltage values from 0 to 10. The mathematics required involves dividing the
decimal number by 250 and then multiplying the result by 10. These calculations
have been approximated in Table 6.3.
Binary
Decimal
Volts
00000000
0
0
00000001
1
0.04
00000010
2
0.08
00000011
3
0.12
00000100
4
0.16
:
:
:
11111001
249
9.96
11111010
250
10
Table 6.3 Digital-to-analog conversion for the example electric motor.
210
Options
If the computer sends a signal of 11111010, it is converted into a voltage of
10 volts in the electric motor.
Transmitting and receiving
In automated manufacturing systems, the transfer of data and information
involves a signal. A signal describes the physical form in which data is transmitted,
such as pulses of electricity in a wire or pulses of light in a fibre-optic cable. Signals
have a physical value that can be sensed and moved from one place to another.
Sensors often generate a very weak signal. This requires the signal to be modified
before a controller can use it. Signal conditioning is the modification of a signal for
normal usage. Amplification is a common signal conditioning technique that
modifies a signal by increasing its strength.
Noise
Signals are affected by noise. Noise is unwanted data or interference that reduces
the quality of the signal. It is often the result of a poorly designed system where
other electrical equipment gives off unwanted high-frequency pulses. There are
two types of noise: random noise and periodic noise. Random noise (or white
noise) is a signal added to the original signal in a random fashion and is usually of
a fairly low value. Periodic (or coloured) noise is a signal with some type of regular
pattern or shape that is added to the desired signal. Shielding surrounding cables
and equipment reduces the problem of noise. For example, the shielding in a
coaxial cable allows data to be transmitted with little distortion.
A signal that is affected by noise needs to be filtered. Filters are used to get rid
of noise and get a smooth signal (see Figure 6.12). Just as filters on a water supply
remove dirt and grease, so electrical filters remove unwanted noise from the signal.
High-pass and low-pass filters are devices that remove frequencies above or below
a certain value. For example, noise might be added to a high-frequency signal. This
noise could be removed by using a high-pass filter that only allows high-frequency
signals to pass. Noise is also reduced by signal conditioning.
(a)
High-frequency
noise level
(b)
Low-frequency
signal from sensor
with noise added
(c)
Signal from
sensor with noise
removed by lowpass filter
Figure 6.12 Filters.
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Noise can cause errors in the transmission of digital signals. Error checking
techniques for digital signals were discussed in Chapter 3. Errors in a digital signal
must first be detected and then corrected. Three common methods for error
detection are parity checking, checksum and cyclic redundancy check.
Exercise 6.4
1
2
3
4
5
6
7
8
9
10
11
12
13
What is mass production?
Outline some of the benefits of mass production.
Describe a trend in mass production.
List three types of production used in automated manufacturing systems.
What is a continuous system?
Outline some of the disadvantages of a batch system.
Describe a discrete system.
What is an actuator?
Briefly describe five different types of actuators.
What is the purpose of a DAC?
Why is signal conditioning often needed in automated manufacturing systems?
Explain the difference between a signal and noise.
Describe two techniques that reduce the problem of noise.
LEARNING ACTIVITIES
1 An automated manufacturing system is being designed to produce kitchen tables
for domestic use. The factory aims to cater for a range of different retailers and
specific requests from its customers. The intended output of the factory is 10 000
tables per year.
a What information is needed to set up the factory?
b One retailer requires 500 identical kitchen tables every year. Describe the
appropriate type of production.
2 A car manufacturer has decided to produce cars that match the exact colour
specifications obtained from its customers.
a Outline any advantages for the customer and the manufacturer for this type of
production.
b Draw a data flow diagram to represent the movement of data.
3 Most of the items we use each day are mass produced.
a List one mass-produced product that you use.
b Describe the automated manufacturing system used to produce this product.
c What actuators are used to manufacturer this product?
4 Use a graphics program to design a robot arm that is able to pick up small items.
On your diagram, show the type and placement of each of the electric motors
used to operate the arm. Indicate the positioning of sensors and the environmental data each sensor is designed to detect (for example, the height of the arm
above a conveyor belt).
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Options
6.5 Issues related to automated
Both positive and negative impacts arise from the use of automated manufacturing systems. In this section, we examine some of the issues raised by automated
manufacturing systems.
Nature of work
have involved replace-ment of people
by an automated system. The longterm effects of automated manufacturing systems on employment are a
debatable issue. People have lost jobs
through automation, but population
increases and consumer demand for
the products have minimised these
losses. Many people argue that
displaced workers should be retrained
for other positions. This argument only
succeeds if the organisation is growing
at a rate fast enough to create new
positions. A worker whose job is taken
over by a machine undergoes a period
of emotional stress. On the other
hand, the use of automation does
create more jobs for people with
information technology skills (see
Figure 6.13).
Figure 6.13 People programming a robot.
Automated manufacturing systems affect not only the number of workers but
also the nature of work. Automation is directed towards the use of information
technology rather than manual labour. It places a greater emphasis on knowledge
and technical skill than on physical work. The types of jobs found in automated
manu-facturing systems include machine operation and main-tenance, operators,
systems analysis and computer pro-gramming. Workers must be technologically
proficient to perform these jobs.
Organisations in the manufacturing industry are making a greater effort in their
job design. For example, operators working on a conveyor can vary their pace by
working ahead and then slowing down, and work breaks occur during production.
Organisations are also beginning to recognise that people have different job needs.
Some people prefer tasks that are repetitive and narrowly skilled. Other people
are bored by repetitive tasks. These organisations are providing opportunities for
job rotation and educational programs to diversify employees’ experience and to
acquaint them with various aspects of the manufacturing process. This will give
each employee a concept of the total manufacturing task and the importance of
each employee’s specific function within that task.
213
Semi-automation
Semi-automation occurs when some tasks are performed by humans and some by
machines. Most factories are only partially automated as they get better results by
only automating some of the functions. For example, in the food industry, a person
inspects the food as it passes along a conveyor belt. Poor-quality items are removed
from production. Another example is the use of machinery to pack and wrap
heavy boxes of the product while people move the boxes using a fork-lift.
ITITFact
Fact
Robots are increasingly being used for many different tasks, from shearing
sheep and washing windows on tall buildings to assembling parts for
machines.
Semi-automation provides advantages to an organisation. The manufacturing
process can be designed to take into account the strengths and weaknesses of
people and machines. People’s strengths are their flexibility, commonsense
and ingenuity. They are better than machines at visualising, understanding and
thinking of new ideas. Machines are better at repetitive tasks and performing
calculations.
Human-centred systems
Machine-centred systems are designed to simplify what the machine must do at
the expense of participants. They assume people will follow confusing procedures
and still work efficiently. If errors occur in a machine-centred system, they are
usually blamed on the participant (operator error) rather than on the technology.
Machine-centred systems are not always the best systems for people. Automated
manufacturing systems consist of many machines; however, the systems should be
human centred.
Human-centred systems are those that make participants’ work as effective
and satisfying as possible. They allow people to do their work without wasting
time and effort dealing with the information technology. Automated manufacturing systems should be designed in consultation with the participants. It is
important that attention is given to the work environment and to the needs of the
participants, as well as to the information technology. An increasing amount of
research has been completed on the relationship between people and machines.
This has led to the improved design of tools, machines and participants’ work
positions.
Reliability and quality
Automated manufacturing systems perform manufacturing processes with greater
control and consistency of product than a human worker. They also make more
efficient use of materials, and this results in less wastage. Machines can repeat a
given task almost endlessly and with a great degree of accuracy. Automated
manufacturing systems can perform repetitive tasks, such as automatic painting,
spot welding and newspaper printing, with a great degree of reliability and
accuracy. They provide an opportunity to relieve people from repetitive,
hazardous, or unpleasant work. The general idea is to free people to do more
challenging and rewarding jobs.
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Options
The reliability and quality of an automated manufacturing system are
dependent on participants. Appropriate procedures need to be in place to ensure
automated manufacturing systems maintain reliability and quality. It is not only
the consistency of the product that is a concern. There are many examples where
lack of quality control has caused a serious accident. For example, the Chernobyl
nuclear-reactor catastrophe in 1987 would have been avoided with better
procedures to test reliability and quality. Machines that are improperly designed
or used kill many Australians each year.
Safety
Automated manufacturing systems have improved safety in the workplace.
Machines are doing dangerous and hazardous jobs, such as spot welding. Most
automated manufacturing systems include safety-monitoring systems. Sensors
detect that a safety condition has developed that may be hazardous to the
equipment or to people. The safety-monitoring system takes the most appropriate
action to remove or reduce the hazard. This may involve stopping the machine
and alerting maintenance personnel, or it may involve a more complex set of
actions to eliminate the safety problem.
On the other hand, unsafe practices and poor machine design can cause
accidents. In dangerous environments, such as near grinding machines, suitable
protective gear should be worn. This would include earmuffs, face masks and
protective clothing made of heavy material. Dangerous machinery should be
shielded from being accidentally touched by workers. General safety issues relate
to adequate lighting, ventilation and fire safety measures. Organisations are
required to provide a workplace that conforms to the Occupational Health and
Safety Act. This act provides heavy penalties for organisations that do not provide
adequate health and safety conditions for their employees.
Case study
Uncle Ben’s Pet Food
Uncle Ben’s Pet Food manufactures such
items as cat food. It is an example of an
automated manufacturing system that uses
robots together with a human controller. A
robot arm examines the boxes of packaged
food going past on the conveyor belt.
When the boxes pass, the robot will inspect
each to see if it is defective in some way.
The defect might be the colour of the
wrapping paper, incorrect alignment of the
labels, incorrect labels, or holes and tears
on the side of the box. The robot has its
gripper over the conveyor belt as the boxes
pass beneath its camera. When a defective
box passes the camera, the robot will grip
the box and then move its arm over a
waste bin where it will let the box fall into
the bin. The arm will then return to its
original position waiting for the next
defective box to be selected. It will repeat
this action over and over again.
Uncle Ben’s Pet Food factory is a continuous production system. Food is manufactured 24 hours a day. People are used to
control the moving conveyor belts and fix
any breakdowns. When they become tired,
there is a greater risk of accidents. For
example, the operator might get careless
and lean too far over the moving belt and
get caught. Uncle Ben’s Pet Food factory
was designed to provide a safe working
environment. For example, the movements
of the robot arm were restricted to ensure
the arm does not move too far away from
the conveyor belt. This is important as it
reduces the risk that a worker will be hit
by the arm. All moving parts have protective covers, and special ‘stop’ buttons
are within reach of the worker to allow for
emergency shutdowns.
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Exercise 6.5
1
2
3
4
5
6
7
8
9
10
11
Describe the effect of automated manufacturing systems on employment.
How are automated manufacturing systems affecting the nature of work?
Describe some of the ways the manufacturing industry is designing jobs.
What is semi-automation?
Describe the advantages of semi-automation.
Outline some ways of designing human-centred manufacturing systems.
List some of the repetitive tasks performed by automated manufacturing systems.
Why are reliability and quality important in an automated manufacturing system?
What is safety monitoring?
Describe some of the ways manufacturing industries can improve safety.
The following questions relate to the Uncle Ben’s Pet Food case study:
a Describe the automated manufacturing system.
b List some of the information technology used in this system.
c Outline some of the safety issues in this system.
LEARNING ACTIVITIES
1 The introduction of information technology into the manufacturing industry has
changed the nature of work. Choose one manufacturing industry and compare
the tasks performed by the employees before and after the introduction of
information technology. What old skills have been lost and what new skills have
been developed in the process of automation?
2 Explain the meaning of the term ‘quality control’ when applied to an automated
manufacturing system. Illustrate your answer with an example.
3 What are some of the safety issues that might effect you at school? Do any of
these issues apply to the workers in an automated manufacturing system?
4 Should workers be trained in first aid at a factory? Who do you think should pay
for this training? Who is responsible for worker safety at a factory?
5 Automated manufacturing systems are having a positive and negative impact on
our society. Briefly describe some of the changes to our society caused by
automated manufacturing systems. What do you think is the greatest concern
with automated manufacturing systems? Give a reason for your answer.
216
Options
Chapter review
PART A
1 The process of producing a product that
meets a specific need is:
A automation
B manufacturing
C automated manufacturing system
D actuator
2 Direct users of an automated manufacturing system do not:
A interact with the information technology
B perform the actual work on the
product
C include supervisors who oversee the
operation
D control the manufacturing system
design and analyse a product is called:
A CAD
B design specifications
C CIM
D IT design
4 A form of programmable automation
in which numbers control a machine is:
A binary code
B automatic code
C NC
D controller
5 A thermistor is a temperature sensor
that:
A measures the temperature using two
different metals in electrical contact
B uses a semiconductor device to
measure temperature
C measures temperature using a
metallic conductor
D uses a liquid or gas to measure
temperature
6 Which of the following terms is not
related to light sensors:
A potentiometer
B photodiode
C CCD
D barcode reader
7 A type of damping that occurs if the
change is too fast and it overshoots the
desired level is:
A fastdamping
B underdamping
C overdamping
D critical damping
8 A batch system is a type of production
that:
A is capable of operating 24 hours
per day for weeks or months without
stopping
B performs a single task in a small time
interval
C produces output usually measured by
volume or weight
D produces a specific quantity of a
product
9 An actuator that consists of a coil of wire
around a movable magnet is called a:
A solenoid
B stepper motor
C relay
D magnetised coil
10 A major problem with mass production
is the:
A standardisation of the parts
B balance between human effort and
machinery
C maximisation of the output
D inflexibility of the system
217
Chapter review
PART B
statement number.
Statements
design and analyse a product or object.
2 A form of programmable automation
in which numbers control a machine.
3 The physical form in which data is
transmitted, such as pulses of electricity
in a wire.
4 A production system that performs a
single task in a small time interval.
5 A display device that performs a
mechanical action under the control of
a signal from a controller.
6 The process of producing a product that
meets a specific need.
7 An information system involved in production by inventory tracking, recordkeeping, production scheduling and
actual production.
8 The use of automatic control for the
storage of products.
9 A system capable of operating 24 hours
per day for weeks or months without
stopping.
10 The specialised information technology
tools that automate the entire manufacturing process.
11 An input device that measures data
from the environment.
12 The process that modifies the signal to
the output device based on the input
signal.
13 A series of workstations connected by a
transfer system that moves parts
between each workstation.
14 The manufacture of products in large
quantities by standardised mechanical
processes.
15 Unwanted data or interference that
reduces the quality of a signal.
218
Options
16 The application of automatic control to
industrial processes.
List of terms
a actuator
b assembly line production
c automated manufacturing system
d automated warehouse
e automation
f CAD
g CAM
h continuous system
i damping
j discrete system
k manufacturing
l mass production
m noise
n NC
o sensor
p signal
PART C
following.
1 What are the characteristics of an automated manufacturing system?
2 Explain the difference between the following terms:
a a continuous and a batch system
b an actuator and a sensor
c CAD and CAM.
3 Outline three reasons for automation.
4 Describe assembly line production.
5 Briefly describe five different types of
sensors.
6 What are the three types of damping?
Briefly explain the differences.
7 Outline one method of removing noise
from a signal.
in automated manufacturing systems.
Identify both the positive and negative
aspects of the issue.
7
chapter
M U LT I M E D I A
SYSTEMS
Outcomes
Overview
multimedia systems, including the different
types of media used in these systems. It
investigates the software and hardware used to
prepare and display multimedia. The information
processes of a multimedia system and the
social and ethical issues related to multimedia
systems are presented.
7.1 Characteristics of multimedia
systems
A multimedia system is an information system that combines different types of
media. It uses at least three media types, such as text, images, animation, audio
and video. Multimedia systems have the potential to provide a better experience
than any other information medium. They can combine the best of television,
film, graphics, animation, books, magazines and radio. The result of a multimedia
system is called a multimedia product or a multimedia presentation. Multimedia
is created and displayed using a range of software, such as authoring software and
presentation software.
Types of media
The types of media used in a multimedia product include text, numbers,
hypertext, audio, images, animations and video.
Text, hypertext and numbers
Text refers to letters, numbers and other characters whose meaning and format is
not specified. It has no meaning until a person reads and interprets it. Text in a
multimedia product is written using a word processor. The first basic concern with
text is how much information should be presented. It is recommended that each
screen should only relate to one task or piece of information. The screen should
not be overloaded with text.
Figure 7.1 A hypertext link.
Hypertext allows the user to navigate through a multimedia product. It is a
system that allows documents to be cross-linked in such a way that the user can
move from one document to another by clicking on a link. A hyperlink (link or
hotword) is the highlighted item (usually an underlined word or a graphic) that
allows the electronic connection (see Figure 7.1). The author of the hypertext
must specify the location of the information accessed by each link. In a multimedia product, the link may be to text, an image, audio, animation or video. When
you click on a link, you move from one document to another even if they are
different media types. Hypertext provides the interactivity in a multimedia
product. The most well-known application of hypertext is the Web.
Numbers refer to predefined characters, usually numerals, whose meaning and
format are specified. Calculations are often performed on this data type. For
220
Options
example, the purchase amount is a number with a predefined dollar format.
Numbers may take different forms but are sometimes linked to some type of chart.
Audio
Audio is sound that has been digitised. The meaning of audio data is determined by
listening to and interpreting the sounds. Audio has become an essential part of
most multimedia products. It is used to explain concepts, reinforce selections and
provide special effects. Sounds may be available in digitised form or may have to be
converted before use. Audio files tend to be large and may be very slow to load in
standard WAV format. The development of the MP3 format for audio has greatly
improved quality and decreased both transmission time and storage requirements.
Images
Images are pictures, such as drawings, paintings or photographs. The meaning of an
image is determined by looking at the image and interpreting it. Images are used
to create interest and provide information. All images on the screen are made up
of tiny dots called pixels. A pixel, or picture element, is the smallest part of the
screen that can be controlled by the computer. The total number of pixels on the
screen is called its resolution. Images are either bit-mapped graphics or vector
graphics.
Bit-mapped graphics treat each pixel on the screen individually and represent
this by bits in memory. They produce good quality images where shading and
detail are needed. However, when transformed (resized or stretched), bit-mapped
graphics become ragged and suffer loss of resolution. Enlarging each pixel in a bitmapped graphic creates a staircase pattern called aliasing. Bit-mapped images
require large amounts of storage. They are often stored in compressed formats,
such as GIF and JPEG.
Vector graphics are made up of objects, such as a straight line, a curve, or a
shape. Each object is defined by its characteristics, such as position, line width, and
pattern. These characteristics are stored as mathematical expressions and
displayed on the screen as pixels. Some common formats for vector graphics
include CGM, EPS and WMF.
ITITFact
Fact
The aspect ratio is the relationship between the vertical and horizontal size
of an image. In normal television, the aspect ratio is 3:4, and in digital
television the aspect ratio is 9:16.
Animation
Animation is the movement of a graphic. It is the result of a series of still images,
or frames, presented in rapid succession. Each frame used in an animation
sequence is called a cell (or cel). The term ‘cell’ derives from the traditional
cartoon frames that were hand-drawn on separate sheets of celluloid. Animations
can present information more effectively than text or an image. For example, an
animation that shows the movement of blood throughout the body is more
effective than a still image. Animations are usually started by entering a page or
clicking a button. Animated GIF and QuickTime are two common formats for
animation.
Multimedia systems
221
Video
Figure 7.2 A video player
in a multimedia product.
Video combines pictures and sounds displayed over
time. It is important to note the difference between
video and animation. Video starts with a continuous
event and breaks it up into discrete frames. Animation
starts with independent pictures and puts them
together to form the illusion of movement. MPEG is a
family of formats for compressed video that has become
a standard for many applications. QuickTime is a video
and animation format developed by Apple Computer. It
is built into the Macintosh operating system and used
with most Macintosh applications. Apple has also
produced a QuickTime version for Windows. Video can
be displayed in a multimedia product by inserting a
video player (see Figure 7.2).
Print and multimedia
The major differences between print and multimedia versions of similar content
are the mode of display and interactivity.
Mode of display
Printed information is displayed using a printer or plotter. In contrast, a
multimedia product is displayed using a screen and speakers:
• A screen is a display surface that provides immediate feedback about what the
computer is doing. It can display text, image, animation and the visual portion
of video data. Every screen is capable of displaying more than one resolution.
The resolution and size of the screen affect the quality of the multimedia
product. Multimedia products are often displayed on an information kiosk. It
allows people to use a touch screen and select information about an
organisation or service.
• A speaker is a device used to produce sounds. A small speaker is usually located
in most personal computers inside the system unit. However, high-quality
stereo speakers are often connected to the computer, using a port and a sound
card, or are built into the sides of the monitor.
Interactivity
A major difference between print and multimedia is interactivity. Interactivity
allows the user to choose the sequence and content of information. A multimedia
product is often judged on the quantity of its interactivity. The Internet is an
example of an interactive environment. The expression ‘surfing the Net’ or
‘browsing’ refers to the experience of jumping from one page to another using
interactivity. Interactive multimedia accepts input from a mouse, touch screen or
keyboard and performs some action. Hypertext and hypermedia are used to
navigate through a multimedia product. The product may link audio, image,
animation, video or another screen. Print provides a limited form of interactivity.
In books, it is possible to choose the sequence and content of the information by
referring to the contents and the index.
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Options
Hardware demands by multimedia systems
The developments in information technology have allowed people to create
multimedia products that were once only developed by film professionals. The
hardware of a multimedia system places limits on the quality and size of the
multimedia product that can be produced or displayed. For this reason, a
multimedia system makes use of the latest technology, such as a fast processor,
large primary storage, high-resolution screen, quality speakers, and the latest in
disk drives.
Image storage
Images place extra demands on the multimedia system including storage. The
current image being displayed is stored in a section of memory called the frame
buffer. When selecting images to include in a multimedia product, it is important
to consider the format of the image and the resolution of the presentation device.
Large high-resolution images may affect the performance of the multimedia
product. An image with high resolution will require more memory than an image
with low resolution. The storage requirements of an image are dependent on the
number, size, tone and colour of each pixel. The relationship between the image
on the screen and the bits in memory is called bit mapping, or memory mapping.
It is dependent on the bit depth.
Bit depth (or colour depth or pixel depth) for images is the number of bits per
pixel. One or more bits must be stored for each pixel on the screen. At the
simplest level, one pixel can represent one bit, where a 0 bit means the pixel is off
and a 1 bit means the pixel is on.
Example: What is the file size in kilobytes of a black-and-white image with a
resolution of 640 by 400 pixels?
File size = Horizontal × Vertical × Bit depth
8 × 1024 bits (= 1 Kb)
= 640 × 400 × 1
8 × 1024
= 31.25 Kb
Bit depth
(bits per pixel)
Number of colours
or tones
Relationship
1
2
21 = 2
2
4
22 = 4
3
8
23 = 8
4
16
24 = 16
6
64
26 = 64
8
256
28 = 256
16
65 536
216 = 65 536
24
16 777 216
224 = 16 777 216
32
4 294 967 296
232 = 4 294 967 296
Table 7.1 Relationship between bit depth and tones or colours.
Multimedia systems
223
Colour graphics and graphics with tones (or grey scale) increase the number of
bits per pixel and require more storage. Colour graphics are obtained from an
RGB (red-green-blue) screen that uses a combination of red, green and blue
colours. The minimum number of colours is eight: red only; green only; blue only;
red and green (yellow); red and blue (magenta); blue and green (cyan); red, green
and blue (white); and no colour (black). For example, as shown in Table 7.1, a bit
depth of 8 allows a graphic to contain 256 colours, or 64 colours each with 4 tones
(64 × 4 = 256), or 32 colours each with 8 tones (32 × 8 = 256). Photo realistic
images require at least 24-bit colour.
Example: What is the file size in kilobytes of a 256-colour image with a
resolution of 1024 by 768 pixels?
File size = Horizontal × Vertical × Bit depth
8 × 1024
= 1024 × 768 x 8
8 × 1024
= 768 Kb
Audio storage
Sound travels through the air in waves with a particular volume and pitch. A
sound wave is analog data. Analog data is represented by continuous variable
quantities while digital data is represented in the form of digits or numbers.
Computers are digital. Audio is sound that has been digitised. It is created using an
analog-to-digital converter (ADC) and reversed by a digital-to-analog converter
(DAC). The ADC and DAC are built into the computer’s motherboard or are
added using a sound card.
The method used by the ADC to digitise a sound wave is called sampling (see
Figure 7.3). Sampling has three important characteristics: the sampling rate, the
sampling size and whether the sound is mono or stereo:
• Sampling rate is the number of times a sample (slice) is taken from the sound
wave. During a sample, the amplitude of the wave (volume) is measured and
converted to a number. Two common sampling rates are 44.1 kHz (44 100
samples per second) and 22.05 kHz (22 050 samples per second). The higher
the sampling rate, the better the sound (see Table 7.2).
• Sample size (or bit resolution) is the number of bits per sample. The most
common sampling sizes are 8-bit sound and 16-bit sound. Better-quality sound
is recorded using 16 bits; however, for most voice uses, 8-bit sound is sufficient.
CD-quality stereo sound requires 16 bits.
Sampling rate
Best uses
11 kHz
Recommended for speech and short segments of music
22 kHz
Better music playback
32 kHz
Broadcast audio standard
44 kHz
CD-quality audio playback
48 kHz
Digital audio tape (DAT) playback
Table 7.2 Sampling rates and their uses.
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Digital audio system
Audio input
Sampling
+3
+2
+1
0
–1
–2
–3
A/D
conversion
0 +2 +3 +2 –1 –3
–2
0
100 110 111 110 011 001 010 100
Disk
Reproduced
signal
D/A
conversion
+3
+2
+1
0
–1
–2
–3
Audio output
Figure 7.3 Sound wave and its digitised form.
• Mono uses one channel of sound, and stereo uses two channels (left and right).
Stereo sound is regarded as the better sound.
An audio file size is calculated by multiplying the sample rate, the sample size
and the time in seconds. If the file is in stereo, then the result of the previous
calculation is multiplied by 2.
Example: Calculate the file size of a CD-quality audio that uses a sample rate
of 44.1 kHz with a 16-bit sample size and a track that lasts for three minutes in
stereo:
File size = (Sample rate × Sample size × time) × 2
= 44 100 × 16 × 180 × 2 bits
= 254 016 000 bits
= 31 752 000 bytes (1 byte = 8 bits)
= 30.28 Mb (1 Mb = 1 048 576 bytes)
The large file size of CD-quality audio has been a problem. MP3 format is a
compressed format that reduces this problem. It filters out superfluous information from the original audio source. This results in smaller audio files with no
apparent reduction in quality. In general, one minute of music equals 1 Mb in an
MP3 file. This can vary depending on the type of compression chosen and the
software used (see Table 7.3).
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225
Audio track time
WAV
MP3
4.11 minutes
42.4 Mb
3.5 Mb
3.33 minutes
36 Mb
3 Mb
8.16 minutes
83.5 Mb
6.95 Mb
Table 7.3 File sizes for WAV and MP3 files.
Video processing
Video can be an excellent medium to explain concepts; however, it places extra
demands on the multimedia system. A decision to use video is often made in terms
of providing exciting additional elements and ensuring the multimedia product
will function effectively. A video camera is used to create a video clip in analog or
digital form. Analog signals need to be converted into digital using a video capture
card. Digital video production software is used to edit the video into a multimedia
product. Editing may involve adding text, audio or images to the video clip. Video
files are usually very large, and this factor must be taken into account before
including them in a multimedia product.
To satisfactorily display video or animations, we need to consider the speed at
which the image can be shown. The speed of a video or animation is called the
frame rate. It is measured by the frames per second (fps). The higher the frame
rate, the smoother the video or animation (see Table 7.4). Full-screen video or
animation requires a fast processor and a lot of random access memory.
Frames per second
Examples
30
Screen refresh rate of monitors
25
Video speed for the PAL system
24
Film speed for motion pictures
12
Cartoon animation speed
8
Minimum speed for the illusion of motion
Table 7.4 Comparison of frame rates.
Large videos and animations can also require large storage facilities. For
example, calculate the file size in kilobytes of a 90-minute movie at 24 fps. Each
frame is 2048 by 872 pixels with 32 bits for each pixel:
Number of frames = (Frame rate x time in seconds)
= 24 × 90 × 60
= 129 600 frames
File size for each frame = Horizontal × Vertical × Bit depth
8 × 1024
= 2048 × 872 × 32
8 × 1024
= 6976 Kb
File size for movie = 129 600 × 6976
= 904 089 600 Kb
= 862.207 03 Gb (1 Gb = 1 048 576 Kb)
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Animation processing
Animation creation is affected by the size of the image and the speed of the
movement. It is frequently set at 30 frames per second, or 9000 frames for a fiveminute animation (30 × 60 × 5). This creates a smooth illusion of movement.
However, drawing 9000 images is a huge task. A computer with animation
software makes this task much easier. Animation is created using path-based and
cell-based animation.
Cell-based animation (or cel animation) involves drawing and displaying
individual frames or cells. Each frame is stored separately and loaded into a
graphics page of primary memory. It is the traditional method of animation. The
animation works by displaying the first frame from a graphics page while creating
the second frame in another graphics page. The second frame is slightly different
from the first frame depending on the items to be animated. The second frame is
then displayed, and the third frame is created in the graphics page of the first
frame. Animation occurs by alternating the display of graphics pages.
This method of animation requires a very powerful computer to achieve
30 frames per second. For example, a high-resolution colour graphic containing
500 000 pixels would require calculations for 15 million (500 000 × 30) pixels in
one second. A fast processor and a large fast-access storage device are required to
ensure that the animation flows at the appropriate speed. For this reason, path-based
animation is preferred.
Path-based animation involves displaying the movement of objects onto a fixed
background in a particular sequence or path. The pixels in the background do not
change, only those for the moving object. This saves memory and processing time.
Animation is achieved by drawing the object, wiping it, and then drawing the
object in a new position. This process is made easier because animation software
can generate the intermediate frames between two objects. This is called tweening
(short for in-betweening). It is a key process in computer animation.
Morphing and warping are animation techniques that create special effects.
Morphing is the smooth change between two different images. It transforms the
shape, size, dimension, and colour of one image into those of another. Morphing
results in one image merging into another (see Figure 7.4). For example, a
Figure 7.4 Morphing.
Multimedia systems
227
Warping involves transforming or distorting a portion of the image. It divides
the image into objects that can be manipulated (see Figure 7.5). For example, a
sad face could be given a smile with the remainder of the face staying the same.
Warping involves one image while morphing requires two images.
Figure 7.5 Warping.
People in multimedia systems
Multimedia products are usually designed by a group of people who have an
expertise in a particular field. Each person works on a different part of the project.
There are people who are responsible for the system design, content and each of
the media types, as well as people with information technology skills. Multimedia
products require careful planning. People involved in multimedia systems include:
• Content providers are people who provide the material for the multimedia
product. This may include text, graphics sketches or final drawings, video
footage and audio tracks. Generally these people are skilled in their field without necessarily having any technical skills in the software or hardware areas.
• The system designer plans and organises the hardware and software required
for the presentation. He or she may also act as the project manager or provide
technical support.
• The project manager organises the scheduling of various components of the
product, provides overall supervision of the components and ensures that all
components are delivered on time.
• The technical staff includes a variety of artists and technicians who edit the
graphic and video material, text and all other material into appropriate formats
for the final document. It also includes layout and design personnel who work
to develop an overall theme and look of the product. These people may also
include the content providers, or they may be a totally separate group.
People may be multi-skilled and work in different aspects of the multimedia
product at the direction of the project manager. The development of any
presentation involves a great deal of planning. This leads into a more detailed
project plan.
228
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ITITFact
Fact
A ‘Webmaster’ is responsible for the coordination of all tasks to keep a Web
site active, secure and functional. The daily operation of a Web site is
completed by a person called a ‘gatekeeper’.
Exercise 7.1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
What is a multimedia system?
List seven different types of media used in multimedia products.
Explain the difference between the media types of text and number.
Describe a hyperlink or hotword.
Why is audio an essential part of most multimedia products?
What are the advantages and disadvantages of a bit-mapped graphic?
Explain the differences between animation and video.
What is interactivity?
Where are current images stored?
Explain the difference between the sampling rate and the sampling size.
What is the frame rate? How is it measured?
Explain the difference between cell-based animation and path-based animation.
Why is tweening a key process in computer animation?
Describe morphing.
Describe the roles of the people involved in producing a multimedia presentation.
LEARNING ACTIVITIES
1 Calculate the size of the following graphics (answer in Kb to the nearest whole
number):
a A black-and-white graphic with a resolution of 640 by 480 and 2 tones
b A colour graphic with a resolution of 1024 by 768 and 64 colours
c A colour graphic with a resolution of 1600 by 1200 and 1024 colours each with
64 tones
d An 8-bit colour graphic with a resolution of 1280 by 1024
e A 32-bit colour graphic with a resolution of 1152 by 864.
2 Calculate the size of the following audio files (answer in Mb, correct to two
decimal places):
a Sampling rate of 22.05 kHz with an 8-bit sound for two minutes in stereo
b Sampling rate of 44.1 kHz with a 16-bit sound for three minutes in stereo
c Sampling rate of 22.05 kHz with a 16-bit sound for one minute in mono
d Sampling rate of 11 kHz with an 8-bit sound for four minutes in mono
e Sampling rate of 44.1 kHz with a 16-bit sound for ten minutes in stereo.
3 Calculate the size of the following video files (answer in Gb, correct to two
decimal places):
a Frame rate of 25 fps, 120 minutes, frame resolution of 1024 by 768 pixels with
16 bits per pixel
b Frame rate of 30 fps, 75 minutes, frames resolution of 1600 by 1200 pixels with
32 bits per pixel
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229
4 The resolution of a screen is set at 640 by 480 pixels. What is the size of the frame
buffer for (answer in Mb, correct to two decimal places):
a 8-bit colour images?
b 32-bit colour images?
5 A shopping centre is creating a multimedia display for an information kiosk. What
types of media could be used in the display? Give an example of the information
to be displayed by each type of media.
6 Multimedia productions, such as television, are being displayed on the Internet.
Outline some of the benefits for users and owners of Internet television over
traditional television.
7 Pauline has scanned a photographic image of her dog. She wants to display the
photograph using 24-bit colour. Is 24-bit colour a suitable bit depth? What file
format would be suitable to save this photograph onto a hard disk with limited
free space? Explain your answer.
7.2 Examples of multimedia systems
Multimedia has developed into a major industry. It is being applied in most areas
of our society, and recent advances in technology are influencing further
multimedia development.
Major areas of multimedia use
There are four major areas of multimedia use: education and training, leisure and
entertainment, information, and virtual reality and simulations.
Education and training
Multimedia systems are very effective at helping people to learn. A good multimedia product that uses different media types can maintain the user’s interest.
The interactive nature of multimedia allows the user to control the learning. It
addresses each user’s particular needs. Multimedia systems also allow training to
be carried out at convenient times and are developed to cater for a wide range of
abilities. They are a cost-effective method of education and training.
Computer-based training (CBT) is a type of multimedia product used for
education and training. A person uses CBT at his or her own pace. Information is
presented using different types of media, and the user has the opportunity to review
misunderstood concepts. CBT products are designed by experts in their fields and
designed to cater for different rates of learning.The ‘Typing Tutor’ is a simple example
of CBT that is designed to improve keyboard skills. Interactivity in CBT is the basis
for an individual to progress through the system. CBT usually contains some form of
assessment to determine whether an individual is ready for the next level.
Leisure and entertainment
Multimedia systems designed for leisure and entertainment are generally classified
as computer games. Computer games provide a high level of interactivity. The
responses of the user determine the game being played.The sequence of actions may
be limited by the game designer or may have a large range of possibilities. Games
tend to be time restricted and have complex animation. The level and amount of
text is limited. Depending on the type of game, the navigation may be deliberately
hidden until the user reaches a certain level. Computer games feature high
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Figure 7.6 Characters from the computer game Carmaggedon.
resolution images, audio, and animation or video. They often use some form of
alternative to the keyboard, such as a joystick, for input. Developments in
technology have resulted in computer games that are more realistic (see Figure 7.6).
Information
Multimedia systems provide users with an easy way to display information. The user
controls when, how and what information will be displayed. The interactive nature
of multimedia allows the user to search using related keywords to find specific
information (see Figure 7.7). This is a distinct advantage over printed forms of the
same material. A multimedia encyclopaedia is a good example of a multimedia
system used to obtain information. It displays information using text, colour, audio,
and video or animation. This makes it easier for people to understand information.
Figure 7.7 The Encyclopaedia Britannica Web site.
Multimedia systems
231
Information kiosks allow people to use a touch
screen and select information about an organisation or
service (see Figure 7.8). The information displayed
depends on the selections of the user. Information
kiosks commonly provide information about items, the
location of items or a map to a particular product or
service. They use large navigation buttons with few
options. Information kiosks can also be used to provide
information to the organisation. The selections made
by the user are a source of information about the level
of interest in a product or service.
Virtual reality and simulations
Multimedia systems are used for virtual reality and
simulations. Virtual reality (VR) is the use of computer
modelling and simulation to enable a person to interact
Figure 7.8 Information kiosk.
with an artificial environment. VR immerses the user in
an environment that simulates reality through the use
of interactive devices, such as goggles, head-up displays, gloves, or body suits (see
Figure 7.9). In a common VR application, the user wears a helmet with a screen for
each eye to view animated images of a simulated environment. Motion sensors that
pick up the user’s movements and adjust the view on the screens create the illusion
of reality. Data-gloves equipped with force-feedback devices provide the sensation
of touch. The user picks up and manipulates objects that he sees in the virtual
environment. VR is highly interactive.
Figure 7.9 Virtual reality mask.
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Flight simulators are used to train pilots. The external effects, such as changing
weather conditions, require high-resolution images and the ability to control
different aspects of the system. Different scenarios are carefully modelled, and the
reactions of the plane are made as realistic as possible. Flight simulators tend to
require a lot of physical room as they involve complex hydraulic systems. This
makes them expensive. However, ‘crashing’ a flight simulator is cheaper than
crashing a real plane.
ITITFact
Fact
Simnet (simulator network) was a network of workstations that enabled
military personnel to practice combat operations on interactive, real-time
training systems. It was used to prepare U.S. troops for the Persian Gulf War
in 1991.
Advances in technology
Advances in technology are influencing multimedia development. For example,
increases in processing speed have allowed video and animation to move at
realistic speeds. The improvements in storage capacity have allowed better-quality
images to be a part of the multimedia production. Dramatic progress in communication technology has allowed multimedia to be displayed on the Internet. It
is now possible to access audio and video over the Internet in real time. Three
significant advances in technology that have influenced multimedia are the World
Wide Web, CD-ROM speed and DVD.
World Wide Web
The World Wide Web (WWW or Web) is an Internet network that allows people
at one computer to collect information stored on another. People connect to other
computers to look at Web sites. A Web site is group of documents that present
information on a particular topic. Each single document is called a Web page.
These Web pages are stored on powerful computers called servers. Each server
stores thousands of Web pages from different Web sites. To view a particular Web
site, the computer connects to the server and receives the Web pages.
The Web is an interactive environment. A hyperlink instantly connects to
another web page with a click of the mouse button. The expression ‘surfing the
Net’ or ‘browsing’ refers to the experience of jumping from one page to another
using hyperlinks. A hyperlink takes the user to another Web site, or another page
within the Web site, or even another location on the same Web page.
Development on the Web has exploded. The increased power of personal
computers and increased speed of access have made the Web a valuable multimedia tool. Organisations and individuals are creating Web sites that contain
multimedia material to present information (see Figure 7.10). This information is
displayed around the world at a reasonable cost.
Multimedia systems
233
Figure 7.10 Web site containing multimedia.
CD-ROM speed
CD-ROM (compact disc with read
only memory) disks are 12 centimetres wide and capable of storing
650 Mb. However, the data is read
only and cannot be changed. CDROMs are convenient for storing
data that remains constant, such as
multimedia applications. A CDROM drive is needed to read data
(see Figure 7.11). The speed of
CD-ROM drives has steadily increased, resulting in faster retrieval
of data. These improvements have
made multimedia products approach a more realistic level.
Figure 7.11 CD-ROM drive.
DVD
DVD (digital versatile disk) is a disk format that can store large amounts of data. It
is an optical disk storage medium that may replace audio CD, CD-ROM, videotape
and video game cartridges. DVD has the ability to produce studio-quality video and
audio. DVDs can store full-length movies. There is DVD Video and DVD-ROM.
DVD Video holds video and is played in a DVD player connected to the
television. Data is compressed (lossy) in MPEG-2 format. However, there is no
noticeable effect on the quality of the video. DVD Video is formatted to play on
either of two mutually incompatible television systems: 525/60 (NTSC) or
625/50 (PAL/SECAM). Video equipment in Australia must conform to the PAL
system, whereas the USA uses the NTSC system.
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A DVD-ROM is the same size as a CD-ROM but provides storage of 4.7 Gb
to 17 Gb. DVD-ROM drives can play CD-ROM and audio CD, and most DVDROM drives will play DVD Videos.
One of the major advantages of a DVD is that text, image, video and audio have
the same file structure. This file structure is called UDF (Universal Disc Format).
This overcomes problems of incompatibility with multimedia applications.
ITITFact
Fact
Polymedia is an advanced and highly sophisticated multimedia system used
in defence, industry and medicine. It uses supercomputers to provide realtime animation and simulation.
Multimedia design
Designing multimedia products involves more than simply using the authoring
software. Good design is critical to the success of a multimedia product. (See
Figure 7.12.)
Figure 7.12 Web site promoting good design.
Design principles
The different media types must be combined into one effective multimedia
product. The design of each screen should be based on the three basic design
principles:
• Consistent. Layout, format and style should be the same throughout the
multimedia product unless different media types demand a change. Readability
is improved when similar items are grouped. Grouping is achieved by spacing,
using colour for the text, changing the backgrounds, or using borders.
• Navigation. People need to understand the structure of the multimedia
product and easily proceed to the desired information. The time the multimedia product takes to respond to a particular action is important. People
become frustrated if they are waiting more than a few seconds for the next
screen or a video clip to load.
Multimedia systems
235
• Simple. Do not use too many design elements as it often confuses the user. The
overuse of colour, sound and animations can be distracting.
Media
Text depends on the purpose, the intended audience and the method of displaying
the multimedia product. There are some generally accepted design principles to
format text:
• Characters. Avoid using too many fonts. San serif typefaces can be clearer than
serif typefaces on the screen. Care should be taken when using font styles such
as bold and italic. Long lines of text are difficult to read. A multimedia product
often uses a larger type size, such as 20 point, than a word processing document would. Headings can be written in serif or san serif typefaces. Different
size headings reflect their importance.
• Screen layout. Appropriate conventions exist for column width, alignment, line
spacing, character spacing, indentation, hyphenation, and kerning. Bullets and
numbering are a common way to organise text in a multimedia product.
• Text colour. Colour contributes to the style and theme of a multimedia
product and draws attention to the text. Some colours should not be used
together as they produce poor contrast and reduce readability (for example,
blue text on a red background). Too many colours can be distracting and
reduce readability. A colour scheme is used to ensure the colours result in a
professional-looking multimedia product.
Images and animations are used to create interest and provide information.
However, they place extra demands on the multimedia system. The position and
size of an image or animation is dependent on its importance and balance with
the other design elements. They can support or weaken a multimedia product.
If too many images are used, they lose their impact. The same goes for animations.
Animations should be used sparingly, such as to introduce a new section within
the multimedia product. Images and animations are edited and adjusted to suit
the screen resolutions. The resolution of an image is dependent on the screen and
the number of colours that can be displayed. The intention of an image must be
easily understood. For example, an image might guide the user to another section
of a multimedia product. Titling is the placement of a caption to accompany an
image or graphic element.
Audio and video are also used to create interest and provide information. An
occasional burst of sound for special effects will focus the audience on the
multimedia. However, the frequent use of sound effects can draw attention away
from the main information. Audio and video can be excellent media to explain
concepts; however, they place extra demands on the multimedia system. Audio
and video files are usually very large, and this factor must be taken into account
before including them in the multimedia product.
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Exercise 7.2
1 Why are multimedia products effective at helping people to learn?
2 Why do computer games have a high level of interactivity?
3 Outline a distinct advantage of multimedia over printed forms of the same
material.
4 What is commonly provided in information kiosks?
5 What is virtual reality?
6 List some of the interactive devices used in VR.
7 How does a flight simulator train pilots?
8 List three significant advances in technology that have influenced multimedia.
9 How is the Web an interactive environment?
10 What factors have made the Web a valuable multimedia tool?
11 Why has the speed of the CD-ROM drive been important in the development of
multimedia?
12 What is DVD?
13 What compressed file format does DVD Video use?
14 Describe a DVD-ROM.
15 Why is UDF an important file structure?
16 Describe three basic design principles for a multimedia product.
17 What are some of the design principles for text colour?
18 What is titling?
19 When should audio and video be used in a multimedia product?
LEARNING ACTIVITIES
1 Multimedia systems perform information processes requiring participants, data/
information and information technology. Clearly identify the participants, data/
information, and information technology in these major areas of multimedia use:
a education and training
b leisure and entertainment
c information
d virtual reality and simulations.
2 Use a multimedia encyclopaedia and a print encyclopaedia to research the same
topic:
a Comment on the similarities and differences between the two encyclopaedias.
b Describe the type of media used in the multimedia encyclopaedia.
c What navigation methods were used in the multimedia encyclopaedia?
d Is it possible to improve on the navigation methods in the multimedia
encyclopaedia? How?
3 Review at least five Web sites that contain different types of media. Comment on
each Web site in terms of design; ease of use; how the media affects the site
operation; and the relevance of audio, video and image files.
4 An interactive multimedia product about your local community is to be created:
a What type of media could be used in the display? Give examples of each type.
b How could the product be interactive?
Multimedia systems
237
c Describe the design features that could be used in the product.
d Design a home screen for this product.
5 A multimedia Web site is to be created to describe the important developments in
computer technology over the last fifty years:
a What type of media could be used in the display? Give an example.
b How could the product be interactive?
c Describe the design features that could be used in the product.
d Design a home screen for this product.
7.3 Displaying in multimedia
systems
Many different tools are used for displaying a multimedia system. Multimedia
systems depend on both hardware and software to create and display different
types of media.
Hardware
The hardware for creating and displaying multimedia includes screens, projection
devices, speakers, CD-ROM, video and head-up displays.
Screens
A screen is a display surface that provides immediate feedback about what the
computer is doing. It can display text, image, animation and video data. The most
common type of screen is a monitor. It uses CRT (cathode ray tube) technology.
CRT displays produce images by firing a stream of electrons onto the inside of
the screen, which is coated with tiny dots or pixels made of phosphor. Monochrome
monitors use one stream, and colour monitors use three streams to strike red, green
and blue phosphor (see Figure 7.13). When the stream of electrons hits the pixel,
the phosphor glows to produce the image. The process by which the colour of a
pixel changes gradually from its original colour to a new colour is called a cross fade.
The total intensity of the pixel usually remains constant during this process.
Three electron guns are located
at the back of the monitor’s
cathode ray tube (CRT).
Each electronic gun shoots
out a stream of electrons,
one stream for each of the three
primary colours: red, blue
and green.
The magnetic deflection
yoke bends the path of
the electron streams.
Figure 7.13 CRT.
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The beams pass through
holes in a metal plate
called a shadow mask,
which aligns them with
their targets on the
inside of the CRT’s
screen.
The electrons strike the
phosphors coating the
inside of the screen,
causing them to glow.
Most CRT displays use a raster scan. A raster scan fires the electron stream in
a series of zigzag lines that starts in the upper left-hand corner and moves left to
right and top to bottom. It is repeated to maintain the image as the phosphor only
glows for a short time. This is called refreshing. Interlaced monitors speed up
refreshing by first scanning the odd lines from top to bottom and then scanning
the even lines. However, this can cause the monitor to flicker. Non-interlaced
monitors refresh the screen by scanning every line at up to 72 times every second.
When the screen is being altered, only the data that is changed is transmitted. The
information that describes the difference between the two screens is called delta
information. It is the ‘change’ information.
A special type of CRT display is available to only display vector graphics.
Vector display systems direct the electron stream to draw only the lines required
for the image. Shading can only be drawn as a series of lines. Vector display
systems have a faster refresh rate than CRT displays using a raster scan.
LCDs (liquid crystal displays)
are a flat screen. They consist of a
layer of liquid crystal material
placed between two polarising
sheets. Light is passed through the
liquid crystal material, and current
is applied at particular points. LCD
technology provides displays that
are very light, take up less room,
produce no heat, have no glare, and
create no radiation. Furthermore,
LCDs require less power than
CRTs, allowing them to run on
batteries. At present, LCD technology does not produce the same
picture quality as CRT technology,
and larger displays are more expensive. LCDs are used in portable
computers (see Figure 7.14) and
can be mounted on the wall.
Touch screens enter data by
detecting the touch of the user’s
finger. The user’s finger interrupts a Figure 7.14 LCD screens used on portable computers.
matrix of infrared light beams
shining horizontally and vertically across the screen. Touch screens do not allow
fine precision of input and use big buttons or areas of the screen.
Projection devices
A data projection panel is a device that can be used together with a standard
overhead projector to project an image from the computer screen onto a wall or
white screen. The projection panel uses LCD technology to display the image
from the computer. Light passes through the image much like a normal overhead
projection slide. Data projectors, which can take a video signal directly from
a computer and project it onto a wall or screen, are also available. They are
smaller and more versatile than a projection panel but are more expensive (see
Figure 7.15).
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Figure 7.15 A data projector.
Speakers
Speakers are devices used to produce sounds. Audio signals from a computer are
translated into analog sound waves for transmission through the speakers. The
sound is generated electromagnetically. A coil of wire is attached to a cone or
diaphragm. The coil is placed around a permanent magnet, so that an electronic
signal passing through the coil magnetises it. As the coil is magnetised, it pulls and
pushes against the permanent magnet, causing the cone to vibrate according to
the strength of the electronic signal. The movement of the cone makes the air near
the cone vibrate, and this creates sound waves.
Head-up displays
Head-up displays are devices worn on the head to display information. They
were originally developed for virtual reality. However, as the technology has
been miniaturised, their application has widened. The heavy helmets have been
replaced by displays no larger than a pair of glasses. In virtual reality, the
participant watches himself or herself reacting to the environment. In other
multimedia systems, the display is projected onto the surface of the glasses. The
participant sees the display overlaying the real world.
ITITFact
Fact
‘There is no reason for any individual to have a computer in their home.’
—Ken Olson, World Future Society Convention, 1977.
Software
The software used for creating and displaying multimedia includes presentation
software, application software, authoring software, animation software, Web
browsers and HTML editors.
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Presentation software
Presentation software is used to make a professional presentation to a group of
people. It improves the communication of information. A presentation consists of
a series of slides. A slide is an individual screen or page of the presentation. Each
slide may contain text, graphics, animation, audio and video. Some popular
presentation software programs include Microsoft PowerPoint, Lotus Freelance
and Aldus Persuasion.
Presentation software creates several documents that are used in a presentation, such as on-screen presentations, audience handouts, overhead transparencies
and speaker’s notes:
• On-screen presentations are slides displayed on a monitor or projected onto a
screen. The timing of the presentation is controlled either automatically or
manually. Automatic timing requires the user to set the timing for each slide;
the slides then advance by themselves. Manual timing requires the user to click
the mouse button to advance each slide.
• Audience handouts are images of two or more slides on a page. Handouts are
given to people who attend the presentation.
• Overhead transparencies are slides printed as an overhead transparency in
black and white or in colour using either portrait or landscape orientation.
• Speaker’s notes are the notes the speaker needs when discussing the slides.
A transition is a special effect used to change from one image or screen to
another. For example, one screen might slowly dissolve as the next screen comes
into view. In general, two or three transitions in a multimedia product will
maximise their impact on the audience. Transitions are frequently used in presentation software to allow a smooth change between slides (see Figure 7.16).
Figure 7.16 A transition design window in PowerPoint.
Application software
Application software is software used for a specific task. A variety of application
software is used in a multimedia system. It is often used to create the different
types of media in the multimedia system. Application software used in multimedia systems includes:
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241
• Word processors allow text to be entered and documents to be created. The
superior editing tools in word processors are used to write the text for a
multimedia system. Some word processors can create documents that include
images and sound.
• Spreadsheets use a rectangular grid made up of rows and columns to organise
and store data that requires some type of calculation. Spreadsheets are also
used to produce different types of charts used in multimedia.
• Graphics software creates and edits images. A paint program creates a bitmapped graphic. A drawing program creates a vector graphic. Images are often
created using advanced graphic tools in graphic software.
• Audio software creates and edits audio. Sounds are edited in many different
ways, such as deleting sounds, changing the speed, adding a echo, overlaying
(mixing) sound files and altering the quality of the sound file.
• Video software creates and edits video. It involves adding text, audio and
images to a video clip. Video software allows for a variety of effects, as well as
the ability to combine segments of different videos into one production. A
frame grabber captures and digitises images from a video. Frames can be cut,
moved, cropped and pasted within the video. Adobe Premiere is an example of
video software (see Figure 7.17).
Figure 7.17 Adobe Premiere.
• Project management software is used to efficiently plan, manage and communicate information on the development of a multimedia project. Project
management software allows projects to be joined, tasks to be split among
team members, and the project to be tracked over the Internet or via email.
Authoring software
Authoring software is used to combine text, graphics, animation, audio and video
into a multimedia product. The software allows the user to bring together the
separate media types. Authoring software allows the user to create interactivity. It
assigns relationships and actions for the different media elements using a scripting
language. Most authoring software shares similar features and is capable of
creating similar multimedia products. Popular authoring software includes
Macromedia Director, Asymetrix Toolbook, Macromedia Authorware, HyperCard
(see Figure 7.18) and HyperStudio.
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Figure 7.18 HyperCard.
Animation software
Animation software takes individual images and creates the illusion of movement. Remember that animation is just a series of images that are displayed in
rapid succession. There are different types of animation software, such as twodimensional (2D) animation, three-dimensional (3D) animation, and warping and
morphing.
• 2D animation software uses flat two-dimensional images and combines them
to create the animation. Macromedia Flash is an example of 2D animation
software.
• 3D animation software uses a mathematical model of a three-dimensional
object to realistically portray objects with depth. It is a common element in
many movies made today.
• Warping and morphing software is used to create special effects using a range
of powerful tools.
Web browsers
A Web browser is a software program stored on a computer that allows access to
the Web. It will display a Web site if the address (or location) is entered directly
into the browser. Web browsers will receive multimedia files that are embedded
in a Web page. Web pages that have multimedia files take longer to download, as
they are larger in size. However, developments in technology are continually
improving the quality and speed of images, audio and video over the Internet.
Some popular Web browsers include Netscape Navigator and Microsoft Internet
Explorer. Both browsers will display a variety of images and can play audio and
video with the appropriate additional software (plug-ins).
HTML editors
Web pages are created using hypertext markup language (HTML). HTML is a
set of special instructions (called tags) that indicate how parts of a document will
be displayed. An HTML editor is a software program that specialises in writing
HTML code. Instructions in HTML are given using HTML tags. Tags are
metadata, or information about data. A tag consists of a left angle bracket (<), a tag
name and a right angle bracket (>). Tags are usually paired such as <TITLE> and
</TITLE> to start and end the tag instruction. The end tag looks like the start tag
except a slash (/) precedes the text within the brackets. Every HTML document
contains certain standard tags, such as <HEAD> and <BODY>. (See Figure 7.19.)
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243
<HTML>
</HEAD>
<TITLE>sample HTML</TITLE>
<BODY BGCOLOR="#FFFFFF">
<H1><CENTER>Pet World</CENTER></H1>
<H3><CENTER>Dogs</CENTER></H3>
<CENTER><TABLE BORDER=1>
<TR>
<TD WIDTH=107>
<P><IMG SRC="dog.gif" WIDTH=94 HEIGHT=183 ALIGN=middle></P>
</TD>
<TD>
<P>Click on the large image to find out more about this breed of dog.
Click on the sound icon to hear the dog barking, or click on the movie
icon to see the dog running.</P>
</TD>
<TD>
<P><IMG SRC="DOGRUN.GIF" WIDTH=200 HEIGHT=35 ALIGN=bottom></P>
<P><IMG SRC="sound.gif" WIDTH=119 HEIGHT=86 ALIGN=bottom></P>
</BODY>
</HTML>
Figure 7.19 An HTML document.
Exercise 7.3
1 How does a CRT display produce images?
2 What is a cross fade?
3 Explain the difference between a CRT display that uses a raster scan and one that
uses a vector display system.
4 Describe an interlaced monitor.
5 How does an LCD display produce images?
6 Describe a data projection panel.
7 How is sound generated in a speaker?
8 Describe some of the documents that can be created using presentation software.
9 List the application software used in a multimedia system. What type of data does
each type of application software create?
10 What is authoring software?
11 List three different types of animation software.
12 How are Web browsers related to multimedia?
LEARNING ACTIVITIES
1 A multimedia presentation is to be created on the requirements of the HSC. The
presentation requires handouts for the audience. What software would you
choose? Why? Describe the processes you would use to create the presentation.
2 Copy and complete Table 7.5 on page 245 by listing the software that is readily
available to create the types of media listed in the first column. If possible, create
a sample file using this software.
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Media
Name of software
Default file format
Text
Audio
Bit-mapped graphic
Vector graphic
Animation
Video
Table 7.5 Types of media.
3 Use audio software and record sound at several different settings. Compare the
quality of the files with the size of the files.
4 Create a multimedia presentation on the content of this chapter (multimedia).
a Use different media types in the presentation.
b Apply good design to the presentation.
c Create a handout of your presentation.
d Show the presentation to the class.
5 Review another group’s multimedia presentation from question 4.
a How effective is the use of the different media types?
b Does the multimedia add to the presentation?
c Does the use of image, audio or video detract from the information being
presented?
d Outline the design principles applied in the presentation.
e What system has been used to help navigate the presentation?
All information processes play a role in multimedia systems, including collecting,
organising, processing, and storing and retrieving.
Collecting
Collecting for a multimedia system may involve a range of tasks, such as writing
the text, drawing images, recording and editing audio files, recording video tracks,
or gathering data from the Internet. It is important to correctly identify the source
and verify the accuracy of any information collected. A range of hardware collection devices is used to collect different media types for a multimedia product.
Methods for digitising
Scanners are input devices that can electronically capture text or images, such as
photographs and drawings. The scanner converts the text or image into digital data
that can be processed by the computer. The digital data can be printed, edited or
merged into another document. Scanners offer a range of different resolutions,
such as 2400 dpi, 4800 dpi and 9600 dpi. The higher the resolution, the better
the quality of the final output. Scanners may be single-pass (scans only once)
or multiple-pass (scans for each colour). They use a software standard called
TWAIN (Technology Without An Interesting Name) that allows the digital image
to be used in a range of different applications. There are three common types
of scanners:
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245
• Hand-held scanners enter text and images
that are less than a page wide. The hand is
used to make a pass of the document. Handheld scanners are adequate for small pictures
and photos but cannot easily capture an
entire page. Software is used to join scanned
items to make a full page.
• Flatbed scanners look similar to a small
photocopier. The document remains flat and
stationary during the scanning (see Figure
7.20).
• Overhead scanners look like an overhead
projector. Documents are placed face up on Figure 7.20 Flatbed scanner.
the scanning bed, and a small overhead
tower moves across the page.
Digital cameras are input devices that capture and store images in digital form
rather than on film. They contain a viewfinder, a lens to focus the image and a
storage medium, such as a memory card, hard disk drive or floppy disk, to retain
the images. After a picture is taken, it is transferred to a computer and can be
manipulated using graphics software. Digital photos are limited by the amount of
memory in the camera, the quality of the lens and the output device. The main
advantage of digital cameras is that making the photos is both inexpensive and fast
because there is no film processing. Most digital cameras compress and save their
images in standard JPEG or FlashPix format.
Video cameras are used to create a video
clip in analog or digital form. Analog form in
a super VHS format is converted into digital
form using a video capture card, which
interprets each frame of the video as a bitmapped image. Video capture cards
compress the video clip by using a
compression algorithm that analyses the
changes from one frame to the next. They
encode the starting frame and a sequence of
differences between the frames. Digital
video cameras are input devices that capture
video in a compressed digital format, such as
MPEG. These video files are transferred
directly to a computer (see Figure 7.21).
A VCR (video cassette recorder) is used
to select footage from existing videotapes.
The final product may also be placed on a
videotape for use. A composite video system
sends all the video information using one
Figure 7.21 Video camera collecting data on road users.
signal. The RCA phono connector is
commonly used for composite video on
VCRs and video cameras. Professional-quality video systems produce two separate
signals: one for colour and one for brightness. Video equipment in Australia must
conform to the PAL system, whereas the USA system is called NTSC. A video
digitiser takes the signal from a single-frame video or videos with a freeze frame
signal. A frame grabber captures and digitises images from a video. The rate of
capture may vary, but usually video frames display at around 30 per second, so a
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freeze frame or frame grabber
system operates by grabbing an
image that lasts for 1/30th of a
second.
Microphones are input devices
that capture sound. Sound travels
through the air in waves and is
analog data. Audio is sound that
has been digitised. A sound card
transforms the sounds from a
microphone into audio. SoundBlaster cards are a standard for
digital audio on a personal computer (see Figure 7.22). They are
capable of recording and playing
digital audio at 44.1 kHz stereo,
or CD-quality sound. Sound cards
support a MIDI sequence. This
allows a musician to use a MIDI
instrument to play music while the
computer can store and edit the
music. Sound may be recorded
onto the computer directly or Figure 7.22 Sound card being inserted into a PC.
imported from storage systems
located on the Internet or on optical disks.
Organising
A script and a storyboard are two tools used to organise a multimedia product. A
script is a printout of all the text, graphics, animation, audio and video used in the
production. It outlines the interactivity in the project. A script gives directions for
the construction of the multimedia product. It is a textual method of representing
ideas and actions. On the other hand, a storyboard is a visual method.
Storyboard
A storyboard is a series of frames each representing a different action or screen
image. It is based on the traditional cartoonist storyboard where the cartoonist
sketches each frame of the cartoon. Storyboards are drawn on paper and frequently edited. They define each screen and the specific media types of the
multimedia product. Storyboards consist of navigation paths, information and
graphics. They are popular because they are simple to construct, easy to read
and can be modified at every stage.
There are four storyboard layouts: (Figure 7.23):
• linear layout—a simple sequential path that is set up quickly
• hierarchical layout—a sequential path in a top-down design in which the user
starts at the beginning and moves down through the multimedia product
• non-linear layout—no structure; the user moves between different layouts in
any direction
• combination layout—a blending of the above layouts.
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247
linear
hierarchical
non-linear
combination
Figure 7.23 Storyboard layouts.
Processing
Processing data for a multimedia system is the manipulation of the data. It
involves the integration of data, compression of data and hypermedia.
Integration of data
After the data is collected, it is often imported into multimedia software.
Multimedia software is used to integrate text, number, image, animation, audio
and video data. It allows the user to bring together the separate media types.
Multimedia software will accept different media types in a variety of formats. It
also allows the user to create interactivity.
Compression and decompression
Multimedia products are characterised by large file sizes. This is the result of
importing large graphics, animation, audio, or video files. Compression reduces the
number of bits required to represent information. It allows the user to store more
data and makes data transfer faster. Compressed data must be decompressed to
extract the original information. There are a number of standard compressed file
formats for different media, such as JPEG for images and MPEG for video.
The use of compressed file formats is very common in multimedia systems.
Images are often stored in GIF or JPEG formats. The major difference between
these formats is the colour support. GIF files are limited to 256 colours, whereas
JPEG images can use the full spectrum of 16.7 million colours. Images are created
using graphics software and saved using one of these formats. This allows them to
be easily imported into an authoring program.
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A CODEC (coder-decoder, pronounced ‘ko-dek’) is used to encode and
decode (or compress and decompress) various types of data. It is typically used for
sound and video files. CODECs convert analog video signals into compressed
video files, such as MPEG, or analog sound signals into digitised sound, such as
RealAudio. The CODEC’s video compression algorithm uses the fact that there
are usually only small changes from one frame to the next to select the data that
can be ‘discarded’ during compression. It encodes the starting frame and a
sequence of differences between frames. CODECs are also used with streaming
(live video or audio).
Hypermedia
Hypermedia involves the linking of information in different types of media. The
information is stored using a set of documents that may contain text, images,
audio, video or executable programs. Each document is independent, and information is retrieved using hypertext. All the various forms of information are
linked together to provide an easy way to navigate. The most well-known
application of hypermedia and hypertext is the Web.
ITITFact
Fact
Click streaming is a technique used to study how individual users navigate
a Web site by recording where they click. Web page designers use it to see
how users are accessing their page and what areas are of interest to the
visitor.
Storing and retrieving
People need efficient methods for the storage and retrieval of information from a
multimedia product. These methods involve different compression techniques
and file formats.
Compression techniques
Compressing files increases the storage efficiency. The amount a file is compressed
is measured by the compression ratio. The compression ratio describes how much
smaller the compressed file is compared to the uncompressed file. If a compressed
file is half the size of the uncompressed file, the compression ratio is 2 to 1 (2:1).
That is, two units of data in the uncompressed file equal one unit of data in the
compressed file. A higher compression ratio indicates greater compression of data.
For example, a compression ratio of 3:1 means the file is more compressed than a
file with a compression ratio of 2:1. A compression ratio of 1:1 indicates the file
has not been compressed at all.
The two basic types of compression are called lossy and lossless:
• Lossy compression removes a number of data bytes from the file. The resulting
file is smaller in size but the quality is reduced. However, audio and video files
can be compressed with high compression ratios and without any change
noticeable to the human ear or eye. For example, an MPEG file can provide a
compression ratio up to 200:1.
• Lossless compression allows the original file to be recovered in full. It works by
replacing repeated data with something that takes up less room. For example,
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249
in this book the word ‘and’ appears many times. If each ‘and’ is replaced with
a one-character symbol or token, two-thirds of the space required by the word
‘and’ is saved. Lossless compression is used mainly on text files, such as word
processing, spreadsheet and database files. Each file of a given type can have a
different compression ratio depending on the contents of the file. A text file
usually has a compression ratio of 3:1.
File formats
It is important to choose an appropriate file format for each type of media. The
application software and the quality of the data will influence the file format. The
type of multimedia product will also influence the file format. For example, if
you were using a Web browser, then images would usually be saved as GIF or
JPEG files. If the multimedia product is to be played as a stand-alone product,
then it must be saved as an application or provided with a player program. It is
also important to store all files on a convenient storage device, such as removable
cartridges (Zip or Jaz disks), optical disks (CD or DVD), flash memory or
videotape.
There are many different file formats used for multimedia. These formats are
constantly changing, and new formats are being developed:
• ASCII (American Standard Code for Information Interchange, pronounced
‘ass-kee’), or TXT (text), format is a standard format for storing text and
numeric data. The data is essentially raw text without any formatting. Each
byte in the file contains one character that conforms to the standard ASCII
code. Most applications can store data in ASCII format.
• RTF (Rich Text Format) is a standard developed by Microsoft for specifying
the format of text documents. RTF files are actually ACSII files with special
commands to indicate the formatting of characters and paragraphs.
• HTML (Hypertext Markup Language) is used to create documents for the
Web. It uses a set of special instructions (called tags) that indicate how parts of
a document will be displayed.
• BMP (Bit-map) is the native bit-mapped graphic format for Microsoft Windows. The images displayed when Windows starts and the wallpaper used on
the desktop are in BMP format. BMP tends to store graphical data inefficiently
with larger file sizes than other graphic file formats.
• JPEG (Joint Photographic Experts Group, pronounced ‘jay-peg’) stores bitmapped graphics. JPEG files are compressed with a compression ratio of up to
100:1. However, JPEG uses lossy compression, so some data is lost during the
process of compression. JPEG format is a popular choice for the Web. It is best
used for photos and continuous tone images. JPEG images can use the full
spectrum of 16.7 million colours.
• GIF (Graphics Interchange Format) stores bit-mapped graphics. It was developed as the predominant format for Web graphics. GIF files can be compressed
to reduce size without loss of quality (lossless compression). It is best used for
line-art drawings, logos and simple graphics. GIF compresses graphics files
using 8-bit colour (256 colours) and achieves a compression ratio of 2:1.
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ITITFact
Fact
A GIF image appears on a Web page in a rough format at first, and then later,
as the page completes loading, becomes clearer and sharper. This method
keeps the viewer interested in the image that is being formatted and makes
the process seem shorter.
• TIFF (Tagged Image File Format) stores bit-mapped graphics. It is widely
supported by applications on both Windows and Macintosh platforms. Some
caution needs to be used when transferring TIFF files across platforms as there
are several variants, some of which involve compression.
• PICT (Picture) stores bit-mapped or vector graphics. It is the standard graphics
file format on Macintosh computers. PICT files are encoded in QuickDraw
commands and can also be used on IBM-compatible computers.
• EPS (Encapsulated Postscript) stores vector graphics. Postscript is a printer
language that is used for high-end publishing. This format is commonly used
for files that will be output on high-resolution devices. EPS files are not viewed
directly on the screen (see Figure 7.24).
Figure 7.24 Software to convert EPS files.
• WMF (Windows Metafile Format) stores bit-mapped or vector graphics. The
WMF file format is commonly used by Microsoft Windows applications. WMF
is used to exchange images between Windows applications.
• CGM (Computer Graphics Metafile) stores vector graphics. It was designed by
several standards organisations to become the standard vector graphics file
format. It is supported by a wide variety of software and hardware products.
• WAV (pronounced ‘wave’) stores either 8-bit or 16-bit sound. It was developed
jointly by Microsoft and IBM and built into Windows. One disadvantage with
WAV sound files is that they require a large file size. For example, a ten-minute
CD-audio sound file will require over 100 Mb.
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• RealAudio is a de facto standard for exchanging sound files over the Internet.
It was developed by RealNetworks and supports FM-stereo quality sound. A
RealAudio player is required to hear a RealAudio sound file on a Web page.
Web browsers such as Internet Explorer and Netscape Navigator include a
RealAudio player.
• AIFF (Audio Interchange File Format) stores 8-bit digitised sound files. It is a
sound file format developed by Apple.
• MIDI (Musical Instrument Digital
Interface, pronounced ‘middy’) is a standard
connection for computers and elec-tronic
musical instruments. A musician uses a MIDI
instrument to play music and uses the
computer to store and edit the music (see
Figure 7.25). MIDI allows 16 instruments to
be played simultaneously from MIDI interfaces. The sound is recorded in a file format
called the MIDI sequence. MIDI files require
less storage as they only contain the note
information and not details of the sound
wave. The quality of the sound from MIDI
files is dependent on the synthesiser.
• MP3 (MPEG Audio Layer 3) is an audio
compression technology that is part of
MPEG-1 and MPEG-2 (discussed below). It
compresses CD-quality sound using a
compression ratio of 11:1. MP3 has made it
possible to download quality audio from the
Internet (see Figure 7.26). For example, a
four-minute song that would normally
require 44 Mb of storage will be compressed
Figure 7.25 Artist recording music in MIDI format.
using MP3 to only 4 Mb. MP3 compresses a
file by removing the high and low frequencies
out of human hearing range.
• MPEG (Motion Picture Expert Group, pronounced ‘em-peg’) is a family of
formats for compressed video that has become a standard. MPEG files achieve
a high compression ratio by using lossy compression and only storing the
changes from one video frame to another. MPEG-1 standard provides a video
resolution of 353 x 240 at 30 fps. It is similar to the quality of conventional
VCR videos. MPEG-2 standard offers resolutions up to 1280 x 720 and 60 fps.
It is sufficient for all major TV standards and is used on DVDs.
• QuickTime is a video and animation format developed by Apple Computer. It
is built into the Macintosh operating system and can be used with most
Macintosh applications. Apple has produced a QuickTime version for
Windows.
• Animated GIF (Graphics Interchange Format) is a type of GIF image that can
be animated. Animated GIF does not give the same level of control as other
animation formats but is supported by all Web browsers.
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Figure 7.26 Web site for MP3.
Exercise 7.4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Describe three common types of scanners.
What is the main advantage of digital cameras?
How does a video capture card work?
What is a composite video system?
What is the usual rate at which a frame grabber captures an image?
Describe four storyboard layouts.
What is compression?
Describe the major difference between GIF and JPEG file formats.
What is the purpose of a CODEC?
What is hypermedia?
Explain the difference between lossy and lossless compression.
What is the difference between an ASCII file and an RTF file?
Describe the JPEG file format.
Describe the EPS file format.
Outline the major difference between MIDI and digital waveform sound files, such
as WAV.
16 Why is MP3 an important file format?
17 Describe two common file formats for video.
LEARNING ACTIVITIES
1 A multimedia production is to be created about your family. What storyboard
layout would be appropriate? Give reasons for your answer. Construct a
storyboard for your family.
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253
2 A multimedia production is to be available on CD-ROM and via the Internet. What
audio and video formats would you choose? Justify your decision. Do these
formats require additional plug-ins?
3 Investigate the current compression formats for video, audio and image files.
Outline the advantages of these formats. Present the results of your investigation
to the class.
4 Create an image using a paint program and a draw program:
a Convert the image to a different resolution and compare the file sizes.
b Convert the image to a different file format and compare the file sizes.
5 A group of students intends to develop a multimedia production about their
school. It is to be displayed on the Web. Outline any problems for users of the Web
site if the multimedia production is developed using a linear layout. What storyboard layout would you suggest for these students?
6 You have been asked to put together a multimedia presentation for a well-known
charity. They are holding a dinner and auction and want to show images of their
work during the meal:
a Describe the hardware you would use to collect information.
b Describe the application software you would use to create or capture the
information.
c List the file formats you would use to store the different types of media.
d Describe the hardware you would need to display the presentation.
e Describe the software you would use to display the presentation.
7 A music store is planning an interactive multimedia Web site of the latest CD
releases using all the media types. The Web site is to include selected songs,
historical data about the artists, photos and interviews. Work in groups to
complete the following tasks:
a Write a storyboard layout for the multimedia display.
b Describe the design features you would use in the production.
c Design a home screen for this display.
d Develop the multimedia product for the Web.
7.5 Issues related to multimedia
systems
Both positive and negative impacts arise from the use of multimedia systems. In
this section, we examine some of the issues raised by multimedia systems.
Copyright
Copyright is the right to use, copy or control the work of authors and artists. It is
against the law to break copyright. You are not allowed to use or copy the work of
another person without the person’s permission. Data collected from the Internet
is usually protected by copyright. Text, images, video or animations obtained from
a Web site should not be used without acknowledgment or permission from the
owner. However, the Copyright Act does make special provisions for students to
use information for research purposes. It allows students to use a reasonable
portion of the original work if correctly cited. When citing an Internet source,
include the following information:
• author’s surname and initial or organisation’s name
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•
•
•
•
title of the completed work or Web page
URL of the page
date of document or Web page publication
download date.
The copyright issue is highlighted with music files. It is legal to rip (the
technical term for transferring songs from standard audio to MP3 format) music
from your own CDs. It is also legal to download music from Web sites where the
artists own the rights. However, playing or distributing any other music files is
breaking the copyright law. Even if you listen to streamed music from a Web site,
the original artist must give permission. The copyright law aims to protect the
original artist for creating the piece of music.
The issue of copyright is a moral issue. Is it right to copy the original work of
an author or artist without their permission? Authors or artists often spend
hundreds of hours developing a product and deserve some return for their efforts.
The fact that it is relatively easy for anyone with a computer to make copies of the
product is irrelevant. If people infringe copyright, authors and artists are not
getting royalties and they will be reluctant to spend time developing good
products. We should take care when downloading files to ensure that they are free
to download or that licensing fees have been paid.
Appropriate use of the Internet
New developments on the Internet
are creating a range of different
issues. The introduction of live
video data raises the issue of
privacy. Privacy is the ability of an
individual to control personal data.
Digital video cameras are being
located in streets and streamed live
on the Internet (see Figure 7.27).
People who are walking down the
street are not aware they are being
photographed nor have they given
permission to be presented on the
video. Is our personal privacy being
invaded? Will all aspects of our
lives, such as work, be streamed
onto the Internet? How can our
privacy be protected from this new
development?
Merging technologies
Figure 7.27 Live video on www.coastalwatch.com.
The merging of different technologies is a trend occurring at a staggering rate.
Today, communication capabilities are essential for a computer system and
computer technology is essential for communication. When people buy a personal
computer, they purchase a modem and connect it to a phone line to access the
Internet. Similarly, telephones have become data entry terminals into computer
systems. Organisations are asking individuals to make choices using the keypad on
the telephone. Radio, television and the Internet are converging. An increasing
number of Web sites are providing radio and video broadcasts (see Figure 7.28).
Will the Internet replace radio and television?
Multimedia systems
255
Figure 7.28 Radio on the Internet.
Advances and cost reductions in processing speeds, storage capacities,
miniaturisation, file compression, and the speed of electrical components have
made the use of digital data more affordable. Digital data is represented in the
form of digits or numbers and is used by computer technology. The digitisation of
data provides the opportunity to use computer technology. Advances in
digitisation have made the extensive use of multimedia feasible. A few years ago
it was not possible for personal computers to combine different types of data. One
example of the benefits of digitisation is digital television.
Digital television systems are designed to present interactive multimedia. They
merge communication, television and computer technologies. Digital television
will offer more channel choices, a higher resolution screen and greater control over
the program the user is watching. For example, a user watching a football match
can choose to watch a particular football player.
ITITFact
Fact
‘The danger from computers is not that they will eventually get as smart as
men, but that we will meanwhile agree to meet them halfway.’—Bernard
Avishai from ‘Charades,’ an Internet collection of quotations.
Data integrity
Data integrity describes the reliability of the data. It involves the accuracy,
currency and relevance of the data. There is no guarantee of the integrity of data
in multimedia systems. The source of any data needs to be cross-referenced. The
Internet is an obvious way of cross-referencing data obtained from a multimedia
system. However, the Internet does not always provide accurate data. Data
integrity raises a number of issues. Who is responsible for the accuracy of the
information? Is the creator the only person responsible for the accuracy of
the data? Do organisations that provide access to information in a multimedia
256
Options
system have a responsibility to verify its accuracy? Responsible users must take
care when obtaining information from multimedia systems. Clearly, it is necessary
to compare data from a number of sources to determine which data is accurate.
Exercise 7.5
1
2
3
4
5
6
7
8
9
What is protected by the copyright law?
List the information needed to correctly cite an Internet source.
How does the copyright issue apply to music files?
Why is copyright a moral issue?
How is live video on the Internet an issue?
Describe the merging of computer technology and communication.
What advances in technology have made digital data more affordable?
List some of the advantages of digital television.
Why is data integrity an ethical issue?
LEARNING ACTIVITIES
1 Multimedia systems are having a positive and negative impact on our society.
Briefly describe some of the changes to our society caused by multimedia systems.
2 Active billboards combined with wireless Internet could allow people to order
items from their car. What issues do you see with this concept? Do you think this
concept will develop in the future? Why?
3 A friend downloaded a multimedia presentation from the Internet and submitted
it to the teacher as her own work. Why is this an ethical issue? What can be done
to stop this practise? Would you take any action? Why?
4 Developments in technology have made huge changes to multimedia systems in
the past five years. Predict some possible changes to multimedia productions in
the next five years. Justify your predictions.
5 Locate and download an MP3 format file with no copyright from the Internet.
Describe this process. What software do you need to play these files on a
computer? Why are musicians and recording companies worried about the MP3
format? Is downloading a song from a Web site the same as stealing? Give reasons
for your answer.
6 You have been asked to update the design of a school Web site. The multimedia
site is to contain some images of the school grounds, staff lists, email contacts for
the school, information about courses, samples of student work and photos of
school activities.
a What privacy issues do you need to consider when showing images of staff or
students?
b How would you ensure that all work displayed is original?
Multimedia systems
257
Chapter review
PART A
1 Which of the following is not a type of
media used in a multimedia product:
A text
B hypertext
C video
D interactivity
2 To produce realistic animation, frames
must be displayed at close to:
A 5 frames per second
B 5 frames per minute
C 30 frames per second
D 30 frames per minute
3 Tweening involves:
A a computer generating intermediate
frames between two objects
B an artist drawing each frame individually
C using cartoon characters in an animation
D creating a path between two objects
4 Morphing is:
A changing one image into another
image
B changing the appearance of one
image
C changing the resolution of an image
D changing the colour depth of an
image
5 The storage requirements for bitmapped graphics will increase if the:
A number of colours increases
B resolution increases
258
Options
6
7
8
9
10
C bit depth increases
D all of the above
A content provider:
A designs the presentation
B often works as project manager
C supplies the material for a presentation
D converts the raw material into digital
format
Virtual reality enables a person to:
A interact with an artificial environment
B interact with the real environment
C select real data for a multimedia
product
D select the content of the information
Which of the following software is not
used to create a multimedia product:
A authoring software
B word processing
C graphics software
D Web browser
When saved to disk, sound may be
stored as:
A WAV, MP3 or RealAudio
B WAV, MPEG or MIDI
C JPEG, RealAudio or MIDI
D JPEG, MPEG or MP3
The most common file format for compressed digitised video is:
A JPEG
B MPEG
C GIF
D MP3
Chapter review
PART B
statement number.
Statements
1 The legal right to ownership of a work.
2 Pictures, such as drawings, paintings or
photographs.
3 The number of bits per pixel.
4 Sound that has been digitised.
5 A file format for images that uses lossy
compression.
6 It is used to create documents on the
Web.
7 A file format for images that uses 8-bit
colour (256 colours).
8 A graphic that is made up of objects,
such as a straight line, curve or shape.
9 A link between two parts of a multimedia product.
10 An audio file format developed by
MPEG.
11 A display that is produced by firing a
stream of electrons onto the inside of
the screen.
12 A device that captures and digitises
images from a video.
13 The number of times a sample is taken
from the sound wave.
14 A graphic that treats each pixel on the
screen individually and represents this
by bits in memory.
15 A type of medium that starts with a
continuous event and breaks it into
discrete frames.
16 The number of bits per sample.
List of terms
a frame grabber
b hotword
c audio
d video
e
f
g
h
i
j
k
l
m
n
o
p
HTML
sample size
GIF
copyright
bit-mapped
vector
CRT
JPEG
image
MP3
bit depth
sampling rate
PART C
following.
1 Describe the different types of media
used in a multimedia product.
2 Compare a multimedia presentation
to a paper-based presentation. Give
advantages and disadvantages for each
version.
3 You have been employed as a project
manager for a multimedia game design
team.
a What is your role in the production?
b Describe the roles of the other members of the team.
c Describe the hardware and software
you will use.
4 Your school is planning a new Web
site. You have been given the job of
designing the site from scratch with a
team of other students.
a What features would you describe as
essential for this site?
b Develop a storyboard for the site.
c Give reasons for your choice of storyboard layout.
d Describe your navigation system.
e Describe the ethical issues that need
to be considered before adding
student photos to the site.
Multimedia systems
259
Glossary
analog-to-digital converter (ADC) A device that
takes an analog signal, such as a voltage or electric
current, and electronically converts it into digital
data.
absolute referencing Copying a formula in a
spreadsheet where the contents of the formula in
the source cell do not change when pasted into the
destination cell. Absolute references are indicated
by a $ sign. (e.g., $B$5).
access See data access.
accuracy See data accuracy.
actuator A display device in an automated
manufacturing system that performs a mechanical
action under the control of a signal from a controller.
aliasing A staircase pattern created when a bitmapped graphic is enlarged.
analog data Data represented by using continuous
variable physical quantities, such as voltages.
analysing The information process that involves the
interpretation of data, transforming it into
information.
analysis report A report that contains details of the
new system with recommendations for design,
implementation and maintenance.
animation The movement of a graphic, as in a
cartoon, accomplished by presenting a series of still
images in rapid succession.
animation software Software that takes individual
images and creates the illusion of movement.
ascending order Data arranged from smallest to
largest (0 to 9) or from first to last (A to Z).
assembly line production A series of workstations
connected by a transfer system that moves parts
between each workstation.
asynchronous transmission Serial transmission
method that sends one byte at a time with special
start and stop bits before and after each byte of
data.
atomicity A property of a transaction processing
system that ensures that all of the steps involved in
a transaction are completed successfully as a group.
attachment A file sent with an email message.
attribute A defined property of an entity in a
relational database.
audio Sound that has been digitised.
audio conference A single telephone call involving
three or more people at different locations.
authoring software Software used to combine text,
graphics, animation, audio and video into a
multimedia product.
automated manufacturing system An information
system involved in production by inventory
tracking, record-keeping, production scheduling
and actual production.
automated warehouse A storage facility that uses
automatic control for the storage of products.
260
Glossary
automation The application of automatic control to
industrial processes. It refers to the application of
machines to tasks once performed by human
beings.
backup A copy of data or software for the purpose
of safety. It is used to rebuild a system.
backward chaining An inference strategy that starts
with one or more possible solutions and searches
back through the system to determine the
questions to be asked.
bandwidth The capacity of a channel, or
transmission medium, to transfer data.
barcode reader An input device that enters product
identification at a point-of-sale terminal.
baseband A network that uses the entire capacity
of the cable to transmit only one signal at a time.
batch system An automated manufacturing system
that produces a specific quantity of a product.
batch transaction processing A transaction
processing method that collects transaction data as
a group, or batch, and processes it later.
baud rate The maximum number of data symbols
or electrical signals that can be transmitted in one
second.
bias Data that is unfairly skewed or gives too much
weight to a particular result.
biometric device A device that uses personal
characteristics, such as fingerprints, hand size,
signature, eye and voice, to gain access to an
information system.
bit depth The number of bits per pixel for an
image.
bit mapping The relationship between the image
and the bits in memory. Also called memory
mapping.
bit-mapped graphic A graphic that treats each pixel
on the screen individually and represents this by
bits in memory.
bit rate See bits per second.
bits per second (bps) A unit of measurement for the
speed of data transfer. It is the number of bits that
can be transmitted in one second. Also called bit rate.
block diagram A diagram used to represent a
system.
bridge A combination of hardware and software
used to link two similar networks.
broadband A network that divides the cable so that
several signals can be transmitted at the same time.
bus A pathway of wires and connectors that
provides the link between input, storage, process
and output devices.
bus topology A network topology where all the
devices are attached to a direct line called a bus.
computer-aided design (CAD) The use of
information technology to design and analyse a
product or object.
computer-aided manufacturing (CAM) The use of
specialised information technology tools to
automate the entire manufacturing process.
computer-based training (CBT) A type of
multimedia product used for education and
training.
cell The intersection of a row and column in a
spreadsheet. Also a frame or still image used in an
animation sequence.
cell reference The position of the cell in the
spreadsheet.
cell-based animation Animation that involves
drawing and displaying individual frames or cells.
character The smallest unit of data that people can
handle. It is a single letter, number, punctuation
mark, or special symbol that can be displayed on
the screen.
chart A graphical representation of numerical data.
Types of charts typically include bar (histogram),
column (stacked bar), line (continuous) and pie
(sector).
checksum A method of checking for errors in data
transmission by counting the number of bits in a
data packet.
computer-integrated manufacturing (CIM) An
automated manufacturing system that involves all
the engineering functions of CAD/CAM, as well as
the business functions of the organisation.
circular reference A formula in a spreadsheet that
refers to itself, either directly or indirectly.
client-server architecture The software relationship
between the client (user) and server.
coaxial cable A cable consisting of a single copper
wire surrounded by an insulator, grounded
shielding and an outer insulator.
coder-decoder (CODEC) A method used to
encode and decode (or compress and decompress)
various types of data.
collecting The information process that involves
deciding what to collect, locating it and collecting
it.
communication system An information system that
enables people to send and receive data and
information.
composite key A key in a database that is made by
joining two or more fields together. It is used when
no data item in any field can be guaranteed to be
unique. Also called compound key.
composite video A system that sends all the video
information using one signal.
compression See data compression.
compression ratio A measurement of the amount a
file has been compressed.
computer operator A person who performs tasks
on the computer equipment, such as monitoring
performance, starting up, running jobs and
backing up.
concurrency A property of a transaction processing
system that ensures two users cannot change the
same data at the same time.
constraint A factor that affects an information
system and prevents it from achieving the
objectives.
context diagram A graphical method of
representing an information system using only a
single process together with inputs and outputs
(external entities).
continuous system An automated manufacturing
system capable of operating 24 hours per day for
weeks or months without stopping.
controller A device in an automated manufacturing
system that receives data from a sensor and
changes it into information that can be used by the
system.
copyright The right to use, copy or control the work
of authors and artists, including software
developers.
cyclic redundancy check (CRC) A method of
checking for errors in data transmission using a
division process.
critical damping Damping at the preferred rate of
change in the output of the system.
cathode ray tube (CRT) A type of screen that
produce images by firing a stream of electrons onto
the inside of the screen, which is coated with tiny
dots, or pixels, made of phosphor.
carrier sense multiple access and collision detection
(CSMA/CD) A method to avoid collisions on an
ethernet network where all nodes have the ability
to sense signals.
custom software Application software written by
programmers using the exact specifications for the
new system.
damping The process in an automated
manufacturing system that modifies the signal to
the output device based on the input signal.
data The raw material entered into the information
system.
data access The extent to which data is available to
people.
data accuracy The extent to which data is free from
errors.
data bits The number of bits in each group of data.
data compression A data storage technique that
reduces the number of bits required to represent
information.
data dictionary A comprehensive description of
each field (attribute) in a database.
data encryption The process of encoding data. It is
the most effective way to achieve data security
during the transmission of data.
data flow diagram (DFD) A graphical method of
representing an information system using a number
of processes together with inputs, outputs and
storage.
data integrity The reliability of the data.
data mart A smaller version of a data warehouse
used to store data about a specific topic or area.
data mining A process that finds relationships and
Glossary
261
data modelling The process of identifying entities,
the relationships between those entities and the
attributes of those entities in a relational database.
data ownership An ethical issue related to who
owns and controls data about an individual
collected by another individual or organisation.
data projection panel A display device that can be
used together with a standard overhead projector
to project an image from the computer screen onto
a wall or white screen.
data redundancy The undesirable duplication of
data within a database.
data security A series of safeguards to protect data.
data type The kind of data, such as image, audio,
video, text or numbers, that can be stored in a
database field.
data validation The checking of the accuracy of the
data before it is processed into information.
data warehouse A database that collects
information from different data sources.
database An organised collection of data.
database information system An information
system that uses a database.
database management system (DBMS) A software
package that builds, maintains, and provides access
to a database.
database of facts Data in an expert system that
relates to the specific situation being analysed.
decision support system (DSS) An information
system that assists people to make decisions by
providing information, models and analysis tools.
decision table A table that represents all possible
conditions and actions. It indicates the alternatives
for different conditions and actions based on the
rules.
decision tree A diagrammatic way of representing
all possible combinations of decisions and their
resulting actions. It represents the decisions made
within a system as the branches of a tree.
decoding The conversion of data from the form
used for transmission back to its original form.
descending order Data arranged from largest to
smallest (9 to 0) or from last to first (Z to A).
digital camera An input device that captures and
stores images in digital form rather than on film.
digital data Data that is represented in the form of
digits or numbers.
direct access A method of retrieving data that
allows data to be found directly, without accessing
all the previous data.
direct conversion Conversion to a new system
involving the immediate change to the new system
on a chosen date and the discontinuation of the old
system.
discrete system An automated manufacturing
system that performs a single task in a small time
interval.
displaying The information process that presents
the output from an information system to meet a
given purpose.
262
Glossary
distributed database A database located at more
than one site that acts as a single collection of data
but is geographically dispersed.
documentation A written description to explain the
development and operation of an information
system.
domain name The address of a specific computer
on the Internet.
downloading The action of receiving a file from
another computer.
electronic mail (email) A messaging system that
allows the sending and receiving of electronic
messages using a computer.
encoding The conversion of data from its original
form into another form for transmission.
encryption See data encryption.
entity A specific thing in a relational database about
which information is collected and stored.
entity-relationship diagram (ERD) A graphical
method of identifying the entities in a relational
database and showing the relationships between
them.
environment Everything that influences or is
influenced by an information system and its
purpose.
ergonomics The relationship between people and
their work environment.
ethernet The first industry-standard local area
network access method, or protocol, based on a bus
topology.
evaluation The process of determining whether the
system is working as expected or whether changes
are required.
expert system An information system that provides
information and solves problems that would
otherwise require a person experienced in that
field (an expert).
expert system shell A ready-made expert system
that contains no knowledge.
explanation mechanism A method of checking how
a deduction was inferred in an expert system.
extranet An intranet that is accessible to customers,
suppliers or others outside the organisation.
feasibility study A short report that analyses
potential solutions and makes a recommendation.
fibre-optic cable A cable that uses a laser of light to
carry data in small glass fibres about the diameter
of a human hair.
field A specific category of data in a database.
field name The name of a field in a database.
field size The number of characters allowed in a
field in a database.
file A collection of information stored on a computer
system and given a name. A file in a database is
made up of records, fields and characters.
file server A controlling computer in a network that
stores the programs and data shared by users.
filter A tool to limit the records viewed in a
database. A tool used to display only the desire
data in a spreadsheet.
firewall A data protection method used on the
Internet or any network to verify and authenticate
all incoming data, including passwords.
flat file database A database that organises data into
a single table.
foreign key An attribute (field) of a table in a
relational database that is a primary key in another
table.
form An arrangement of fields on the screen, often
from a single record, that is used to view, enter, and
change data in a database. Also a document used to
collect data from a person.
formula An instruction to perform a calculation in a
spreadsheet.
forward chaining An inference strategy in which
the user supplies all the data before the question is
asked or the inference is made.
frame buffer A section of memory that stores the
image currently being displayed.
frame grabber A tool used to capture and digitise
images from a video.
frame rate The speed of a video or animation,
measured in frames per second.
full-duplex mode The transmission of data in both
directions at the same time.
function A predefined set of operations in a
spreadsheet that perform simple or complex
calculations.
fuzzy logic A term used to describe the variables
that exist between a ‘true’ and a ‘false’ situation in
an expert system or neural network.
Gantt chart A bar chart with each bar representing
a task or stage in the system development cycle. It
provides a quick method of determining whether
the project is on schedule.
gateway A combination of hardware and software
used to link two different types of networks.
grandfather-father-son A backup procedure that
refers to at least three generations of backup
master files.
graphic A picture, such as a drawing, painting, or
photograph.
group decision support system (GDSS) An
information system that assists users to make a
decision by working together in a group.
half-duplex mode The transmission of data in both
directions but not at the same time.
handshaking The sending of signals to reach an
agreement about which protocol to use to
accomplish an exchange of information.
hard disk A disk made of metal or glass and covered
with magnetic material. It is used to store data.
hardware flow control A handshaking method that
uses a dedicated connection, such as a wire, to
control the flow of data.
head-up display A device worn on the head to
display information.
hierarchical database A database that organises data
in a series of levels.
hypertext markup language (HTML) A set of
special instructions (called tags) that indicate how
parts of a document on the Web will be displayed
and navigated.
HTML editor A software program that specialises
in writing HTML code.
HTML tag An instruction in HTML.
hub A central connecting device in a network. Data
arrives at the hub from one or more devices and is
forwarded out using just one cable.
human-centred system A system that makes
participants’ work as effective and satisfying as
possible.
hyperlink The highlighted item (usually an
underlined word or graphic) that allows an
electronic connection between documents in a
hypertext system. Also called link or hotword.
hypermedia A combination of media whose
locations are linked to provide an easy way to
navigate between the documents.
hypertext A system that allows documents to be
cross-linked in such a way that the user can move
from one document to another by clicking on a
link.
image Data in the form of a picture, such as a
drawing, painting or photograph.
implementation plan A document that details the
participant training, method of conversion and
testing for a new information system.
indexed access Direct access that involves the use
of an index.
inference engine A set of routines in an expert
system that carries out deductive reasoning by
applying the facts, assumptions, theories, and rules
in the knowledge base.
information Data that has been ordered and given
some meaning by people.
information kiosk A multimedia device that allows
people to use a touch screen and select information
about an organisation or service.
information processes The steps taken to change
data into information: collecting, organising,
analysing, storing/retrieving, processing,
transmitting/receiving and displaying.
information processing The creation of information
by processing data using information technology.
information system A set of information processes
requiring participants, data/information and
information technology. It is created for a purpose
and to operate in a particular environment. It
performs the seven information processes.
information technology The hardware and software
used by an information system.
intelligent agent A piece of software used to search
through relational databases for relevant data.
intelligent system A system that receives data from
the environment, reacts to that data and produces
an intelligent response.
interactivity The property of an information system
that allows the user to choose the sequence and
content of the information to be displayed.
Glossary
263
Internet A global collection of computer networks
that speak the same language and are hooked
together to share information.
intranet A private network that uses a similar
interface to the Web.
key A field in a database that is used to sort and
retrieve information.
knowledge base A set of general facts and if-then
rules supplied by an expert and forming part of an
expert system.
knowledge engineer A person who builds an expert
system.
label Text entered into a cell of a spreadsheet to
provide some explanation of the spreadsheet.
link See hyperlink.
liquid crystal display (LCD) A display device that
consists of a flat screen formed from a layer of liquid
crystal material placed between two polarising sheets.
local area network (LAN) A network that connects
computers (or terminals) within a building or
group of buildings on one site.
logical operator A series of characters or a symbol
used to combine simple queries.
logon The procedure used to get access to the
network.
lossless compression A type of compression that
works by replacing repeated data with something
that takes up less room.
lossy compression A type of compression that
removes a number of data bytes from the file.
machine-centred system A system designed to
simplify what the computer must do at the
expense of participants.
macro A series of commands stored in a file that
can be executed by pressing a few keys.
magnetic disk A circular piece of metal or plastic
whose surface has been coated with a thin layer of
magnetic material. It is used to store data.
magnetic tape A very long, thin strip of plastic,
coated with a thin layer of magnetic material. It is
used to store data.
mail server A computer in a network that provides
email facilities.
maintenance The modification of the system by
making minor improvements.
management information system (MIS) An
information system that provides information for
the organisation’s managers. It presents basic facts
about the performance of the organisation.
manufacturing The process of producing a product
that meets a specific need.
mass production The manufacture of products in
large quantities by standardised mechanical
processes.
messaging system A system used to send messages
to people in different locations who can receive the
message at a different time.
metadata Information about data.
magnetic ink character recognition (MICR)
Characters written using magnetic ink that
264
Glossary
contains magnetised particles. It is widely used by
banks to print serial numbers on cheques.
microwave A high frequency radio signal sent
through space in a straight line from one antenna
to another.
model A representation of some aspect of the real
world.
modem A device that enables the transmission of
data from one computer to another.
morphing Animation technique that involves
the smooth change between two different
images.
multimedia The presentation of information using
text, graphics, animation, audio and video.
multimedia system An information system that
combines different types of media.
MYCIN A famous expert system designed to assist
non-specialist doctors in the diagnosis and
treatment of bacterial blood infections.
network A number of computers and their
peripheral devices connected together in some
way.
network administrator A person who manages a
network within an organisation.
network database A database that organises data as
a series of nodes linked by branches.
network interface card (NIC) An expansion card
that fits into an expansion slot of a computer or
other device, so that the device can be connected
to a network.
network licence A licence that allows people to use
a program on a network.
network operating system (NOS) An operating
system that is designed primarily to support
computers connected on a LAN.
network topology The physical arrangement of the
devices on a network.
neural network An information system that works
like the human brain and is capable of learning.
newsgroup A discussion group where people can
read messages and join in discussions by sending or
posting messages.
node A device in a network.
noise Unwanted data or interference that reduces
the quality of a signal.
normalisation The process of organising data into
tables so that the results of using the database are
unambiguous and as intended.
number A data type consisting of predefined
characters (usually numbers) whose meaning and
format are specified.
numerical control (NC) A form of programmable
automation in which numbers control a machine.
office automation system An information system
that provides people with effective ways to
complete administrative tasks in an organisation.
offline storage The use of a peripheral device that is
not under the user’s direct control to store data.
online storage The use of a peripheral device that is
under the user’s direct control to store data.
operation manual A document containing detailed
procedures for participants to follow when using a
new system.
optical disc A polycarbonate plastic disk the surface
of which is covered with a reflective layer of metal.
It is used to store data.
organising The information process that involves
the modification of data by arranging, representing
and formatting.
overdamping Damping that occurs if the change is
too slow and the actuator takes longer to reach the
desired level or position.
ownership See data ownership.
packet switching A data transmission technique
that divides messages into small data packets,
transmits the packets and later joins the packets to
form the original message.
parallel conversion Conversion to a new system
involving the old and the new system both working
together at the same time.
parallel transmission The transmission of data
simultaneously using separate channels.
parameter A variable that is given a constant value
for a particular application.
parity bit An additional bit attached to the binary
code for each transmitted character whose purpose
is to check the accuracy of the received character.
parity checking A method of checking for errors in
data transmission using an additional bit called a
parity bit.
partial backup A backup that only stores parts of
the master file.
participant A person who carries out the
information processes within an information
system.
participant development The development of an
information system by the people who will use it.
path-based animation Animation that involves
displaying the movement of objects onto a fixed
background in a particular sequence or path.
phased conversion Conversion to a new system by
gradually implementing the new system.
pilot conversion Conversion to a new system by
trialing the new system in a small portion of the
organisation.
pivot table An interactive table in a spreadsheet
that quickly summarises large amounts of data.
pixel The smallest part of the screen that can be
controlled by the computer.
port A socket used to connect peripheral devices.
preliminary investigation The process of
determining whether a quick fix of the existing
system will solve the problem or a new system is
necessary.
presentation software Software used to make a
professional presentation to a group of people.
primary key A single key or compound key in a
database that must have a value; i.e., it cannot be
empty or null.
primary source Data collected first hand.
print server A computer in a network that controls
one or more printers and stores data to be printed.
privacy The ability of an individual to control
personal data.
processing The information process that involves
the manipulation of data and information.
programmable logic controller (PLC) A computer
that performs the timing and sequencing functions
required to operate industrial equipment in an
automated manufacturing system.
programmer A person who converts a written
description of a problem into a set of computer
programs.
project leader A person who develops schedules,
checks work and resolves conflicts for a project
team. Also called project manager.
project management The process of planning,
scheduling and controlling all the activities within
each stage of the system development cycle.
project plan A summary of a project that specifies
who, what, how and when.
protocol In data transmission, a set of rules that
governs the transfer of data between computer
devices.
prototype A working model of an information
system built in order to understand the
requirements of the system.
query A search of a database for records that meet a
certain condition.
query by example (QBE) A common method for
describing a query. It requires the user to enter the
criteria against a field.
query language (QL) A specialised language
designed to allow users to search for information
from a database.
random access See direct access.
range A group of cells in a single row or column or
in several adjacent rows and columns of a
spreadsheet.
raster scan A device that fires an electron stream in a
series of zigzag lines to produce an image on a
screen.
real-time transaction processing A transaction
processing method that processes data
immediately.
record A collection of facts about one specific entry
in a database.
refreshing The process of maintaining an image on
a screen by repeating a raster scan.
relational database A database that organises data
using a series of related tables.
relational operator A character or a symbol
indicating the relationship between two
expressions in a query.
relationship The way entities are related to each
other in a relational database. Relationships can be
one to one, one to many, and many to many.
relative referencing Copying a formula in which the
cell references change so that they relate to the
destination.
Glossary
265
removable cartridge A hard disk encased in a metal
or plastic cartridge that can be removed like a
floppy disk. It is used for data storage.
repeater A device used during the transmission of
data to rebuild a fading signal to its original
strength and shape.
report A formatted and organised presentation
of data.
requirement definition See preliminary investigation.
requirement report A statement about the need for
a new system.
resolution A measurement of the detail of an image
produced on a screen or output to a printer.
response time The amount of time taken by the
computer to respond to a command.
ring topology A network topology in which all
devices are attached so that the path is in the shape
of a continuous circle.
router A device that determines where to send a
data packet between at least two networks.
sample size The number of bits per sample. Also
called bit resolution.
sampling The method used to digitise a sound
wave.
sampling rate The number of times a sample (slice)
is taken from the sound wave.
scanner An input device that can electronically
capture text or images, such as photographs and
drawings.
schema An organised plan of the entire database
showing how and where the data is found,
descriptions of the data and the data’s logical
relationships.
schematic diagram A graphical tool to help define a
database and develop a schema.
screen A display surface that provides immediate
feedback about what the computer is doing.
search engine A database of indexed Web sites that
allows a keyword search.
search robot A program that accesses Web sites and
gathers information for search engine indexes.
searching The process of examining the database to
retrieve data.
secondary key A field in a database that contains
useful items of data, not necessarily unique and
often used in searches.
secondary source Data that is collected or created
by someone else.
sensor An input device that measures data from the
environment, such as temperature, pressure,
motion, flow and light. Also called transducer.
sequential access A method of retrieving data that
searches the storage medium from its beginning
and reads all the data until it finds the desired data.
serial port A type of port that transmits data one bit
at a time using only one communication line.
serial transmission The transmission of data one
after the other.
server A computer that provides services to other
computers on the network.
266
Glossary
signal The physical form in which data is
transmitted, such as pulses of electricity in a wire
or pulses of light in a fibre-optic cable.
signal conditioning The modification of a signal for
normal usage.
simplex mode The transmission of data in one
direction only, from the sender to the receiver.
simulation The use of a model.
single key A field in a database in which each item
of data is unique.
software flow control A handshaking method that
uses a special code sent with the data to control
the flow of data.
software package Application software bought to
cover most requirements.
sorting The process of arranging data in a particular
order.
sound card An expansion card that transforms the
sounds from a microphone into audio.
speaker A device used to produce sounds.
spreadsheet A rectangular grid made up of rows
and columns to organise and store data that
requires some type of calculation.
structured query language (SQL) A query language
used to access and manipulate data in a relational
database.
star topology A network topology that has a central
computer with each device connected directly to it
but not to one another.
storing and retrieving The information process that
involves saving data and information for later use
(storing data) and obtaining data and information
that has been previously saved (retrieving data).
storyboard A series of frames, each representing a
different action or screen image. It shows the
navigation between frames.
switch A device that directs data packets along a
path.
synchronous transmission Serial transmission
method in which data is all sent at the same rate;
i.e., the same number of bytes is sent each second.
system A group of elements that work together to
achieve a purpose.
systems analyst A person who performs the analysis
to decide whether a new or updated system will
solve the problem.
system development cycle A traditional method for
developing a new information system.
system flowchart A graphical method of
representing both the flow of data and the logic
of a system.
table In a document, rows and columns of cells that
are filled with text and graphics. In a database, the
organisation of data into columns (fields) and rows
(records).
technical support staff People who assist
participants of a system on an as-needed basis.
teleconferencing The use of an electronic
transmission to allow a meeting to occur at the
same time in different locations.
template A document created for repeated use.
terminal A device used to send data to and receive
data from another computer system.
test data A range of data values structured to test all
decisions made within an information system and
to cover all possible combinations of data that may
be encountered.
text A data type consisting of letters, numbers and
other characters whose meaning and format are not
specified.
titling The placement of a caption to accompany an
image or graphic element.
token ring A local area network access method, or
protocol, based on a ring topology.
top-down design The process of dividing a large,
complicated problem into a series of smaller, easier
to solve problems.
topology See network topology.
training specialist A person who teaches
participants how to operate their system.
transaction An event that generates or modifies
data that is eventually stored in an information
system.
transaction processing monitor Software that
allows transaction processing application programs
to run efficiently.
transaction processing system (TPS) An
information system that collects, stores, modifies
and retrieves the daily transactions of an
organisation.
transition A special effect used to change from one
image or screen to another.
transmitting and receiving The information process
that involves the transfer of data and information
within and between information systems.
tuple A row in a table of a relational database.
tweening The process of taking two images of an
animation and producing intermediate images so
that the animation is smoother.
twisted-pair A cable that consists of two thin
insulated copper wires, twisted to form a spiral.
underdamping Damping that occurs if the change
is too fast and the actuator overshoots the desired
level.
uploading The action of transferring a file from the
user’s computer to another computer.
uniform resource locator (URL) The address of a
file or resource on the Web.
user-friendly A term used to describe a tool that
people find easy to use.
value A number stored in a spreadsheet on which
calculations are carried out.
vector display system A special type of cathode ray
tube display that only displays vector graphics. It
directs the electronic stream to draw only the lines
required for the image.
vector graphic A graphic made up of objects, such
as a straight line, curve, or shape.
video A data type that combines pictures and
sounds displayed over time.
video conference A meeting that allows people at
different locations to see video images of each
other on a screen, as well as to hear speech.
virtual reality The use of computer modelling and
simulation to enable a person to interact with an
artificial environment.
voice mail (v-mail) A messaging system that allows
communication with other people by storing and
forwarding spoken messages.
wide area network (WAN) A network that
connects computers (or terminals) over hundreds
or thousands of kilometres.
warping An animation technique that involves
transforming or distorting a portion of an image.
World Wide Web (Web or WWW) Part of the
Internet and the most user-friendly way to access
the Internet.
Web browser A software program stored on a
computer that allows access to the Web.
Web page A single document on a Web site, usually
in HTML format.
Web server A computer in a network that provides
a connection to the Internet.
Web site A linked collection of Web pages by the
same organisation or person.
‘what if’ The process of making changes to the data
in a spreadsheet and observing the effects of those
changes.
wildcard character A character that represents one
or more unknown characters in a search or query.
workstation An intelligent terminal, such as
personal computer, in a network.
Glossary
267
Index
absolute referencing 162–3
acceleration sensors 201
accuracy of data 69, 141–2
active listening 6
actuators 188, 209–10
AIFF (Audio Interchange File Format) 252
aliasing 221
analog data 100
analog-to-digital conversion 204–5, 224
see also digital-to-analog conversion
analysis report 17
Animated GIF (Graphics Interchange Format) 252
animation 221, 236
cell-based 227
file formats 252
path-based 227
processing 227–8
software 243
application software, multimedia 241–2
ASCII 250
assembly line production 192–3
asymmetric encryption 55
asynchronous transmission 87, 88
attachments, email 102
attribute 44
audio 221, 236
conference 81
file formats 251–2
software 242
storage 224–6
authoring software, multimedia 242–3
automated manufacturing systems
assembly line production 192–3
automated warehouses 193
CAD/CAM 193–4
characteristics 187–91
data collection 198–205
human-centred systems 214
and information display 208–11
mail sorting 195
reliability and quality 214–15
safety 215
semi-automation 214
and work 213
automated warehouses 193
automatic teller machine (ATM) 135
automation
defined 187
of jobs 139–40
reasons for 195–6
backup 56, 128–31
backward chaining 168–9
banking
and decision support systems 152
Internet 106–7
bandwidth 77
bar charts 174
268
Index
barcode readers 135, 202–4
baseband transmission 95
batch transaction processing 114–15, 116–17,
124–5, 130–1
see also real-time transaction processing
baud rate 78
bias 141
bill generation 124
bit
depth 223
mapping 223
bit-mapped graphics 221
file formats 250-–1
bits
data 79
stop/start 79
bits per second (bps) 78, 79
block diagram 190–1
BMP (Bit-map) 250
bridges 93–4
broadband transmission 95
bus topology 92
CAD/CAM 193–4, 198–9
cameras 246
car industry 192–3
CD-ROM speed 234
cell 221
cell-based animation 227
censorship 106
CGM (Computer Graphics Metafile) 251
characters 43, 236
charge-coupled devices (CCD) 202
charts 156, 173–4
check digit 69
cheque clearance 124
checksum 78
CIM (computer-integrated manufacturing) 199
client-server architecture 102
coaxial cable 95
CODEC (coder-decoder) 249
collecting data 100, 134–7, 176–8, 188,
198–205, 245–7
colour graphics 223
column charts 174
communication
concepts 87–98
skills 6
settings 79
systems 76–86, 104–8
composite
key 44
video system 246
compression 248–9
ratio 249
techniques 249–50
computer
games 230
operators 30
computer-based training (CBT) 230
confidentiality 104
conflict resolution 6
constraints 15
content provider 228
context diagrams 20–1
controller 188
conversion method 27–8
copyright 254–5
credit cards 125
cross fade 238
CRT displays 238
CSMA/CD 92
cyclic redundancy check (CRC) 78
damping devices 205
data
access to 70–1
accuracy 69, 141–2
analog 100
analysing 137–8
bits 79
collection 100, 134–7, 176–8, 188, 198–205
digital 101–2
extracting summary 172
filtering 172
flow 88
identification 176–7
importance of 141–2
integration of 248
integrity 70, 142, 256–7
management 148, 149
matching 175
methods of accessing 54
modelling 47–9
ownership of 71
processing 100–2, 188, 207–8
range 176
redundancy 48
security 56, 141
storage and retrieval 53–62, 126–33, 178
structured 176
transmission 87–98, 211–12
type 47
unstructured 176, 180
validation 69, 117
data dictionary, 23, 47–8
Data Encryption Standard (DES) 56
data flow diagram (DFD) 21–2
data mart 156
data mining 71, 138, 171–2, 180–1
data projection panel 239
data projectors 239–40
data sources 69, 76, 160
primary 176
secondary 176
data warehouse 71, 127–8, 156
database information systems 38–9
database of facts 167
database management systems (DBMS) 53–4, 55
56
databases
constructing different views 65–6
distributed 54–5
defined 126, 156, 175
and files 126–7
flat file 43–4
relational 44–7
decision
making 15–18, 180, 182
tables 22–3
trees 22–3
decision support systems (DSSs) 37, 137–8
and analysing 171–5
characteristics of 147–51
issues related to 179–82
nature of 147–9
and organisation 159–65
and processing 167–70
semi-structured situations 149–50, 152–3
structured situations 149
types of 154–8
unstructured situations 150–1, 153, 180
decoding 100–2
decompression 248–9
delta information 239
design
multimedia 235–6
principles 235–6
social and ethical 8–12
solutions 18–25
specifications 17
of systems 8–9
tools 20–5
dialogue management 148, 149
digital
cameras 246
data 101–2
television 256
digital-to-analog conversion 210–11, 224
see also analog-to-digital conversion
digitising 256
methods for 245–8
direct
access 54
conversion 27
users 188–9
directories 61
displaying 64, 102–3
in multimedia systems 238–44
distributed databases 54–5
domain/key normal form (DKNF) 49
DVD 234–5
economic feasibility 16
education and multimedia 230
EFTPOS 85, 103
electric motors 209
electronic banking 85–6
electronic commerce (e-commerce) 85
electronic junk mail 104
electronic mail (email) 82–4
employment and automation 139–40, 213
see also work
Index
269
encoding 100–2
encryption 55–6
entertainment and multimedia 230
entity 44
entity-relationship diagram (ERD) 48
environment 10–11
EPS (Encapsulated Postscript) 251
equity 11–12
ergonomics 9–10
erroneous inferences 181
error checking 78
ethernet 92
ethical design 8–12
ethics 10
evaluation, system 30
expert knowledge 180
expert systems 37, 156–7, 167–8, 175, 177
shells 164
explanation mechanism 168
extranet 98
fax 81–2
feasibility study 15–16
fibre-optic cable 95
field 43
name 47
size 47
file 43
formats 250–2
filters
data 172
noise 211
firewall 56
First Norm Form (1NF) 49
flat file databases 43–4
flight simulators 233
flow
control 79
sensors 201
flowcharts, system 24–5
foreign key 46
forms
on-screen 46, 136–7
paper 135
Web 137
formulas 155, 161–4
forward chaining 168, 169
frame
buffer 223
grabber 246–7
rate 226
full-duplex mode 88
functions, spreadsheet 162–3
furniture 9
fuzzy logic 169–70
Gantt chart 5
gateways 93–4
gender equity 11–12
geographic information system (GIS) 153–4
ghost site 70
GIF (Graphics Interchange Format) 250–1
grandfather-father-son backup procedure 130
270
Index
graphics
colour 223
file formats 250–1
software 242
group decision support system (GDSS) 181–2
half-duplex mode 88
handshaking 77, 88–9
hard disk 55
hardware
data collection 134–5
flow control 77
and multimedia systems 223–8, 238–40
network 92–6
head-up displays 240
health and safety 9–10
heuristic rules 177
HTML 51–2, 250
editors 243–4
hubs 94
human-centred systems 8, 214
hydraulic pump 210
hyperlink 49, 220
hypermedia 49, 60–2, 249
hypertext 49, 220
identification of data 176–7
image storage 223–4
images 221, 236
implementation 26–8
index 54, 60
indexed access 54
inference engine 167–9
information
kiosks 232
management software 4
and multimedia 231–2
processes 36, 64–7, 100–3, 134–8, 176–8,
207–12, 245–53
information systems 36–9
characteristics 36
database 38–9
types and purposes 37–8
intelligent
agents 171, 178
systems 179–80
interactive environment 233
interactivity 147, 222
Internet 105–7
appropriate use of 255
banking 106–7
and censorship 106
radio and video 107
trading 105
Internet Industry Association (IIA) 106
interview techniques 6
intranet 98
inventory tracking 202–4
jobs see employment
journal 129
JPEG (Joint Photographic Experts Group) 250
keys 43–4
knowledge
base 164–5, 167
engineers 177
expert 180
label 154
LCDs (liquid crystal displays) 239
leisure and multimedia 230
library loan system 123
light sensors 201–2
line charts 174
linear regression models 173
link see hyperlink
list check 69
live video 255
local area networks (LANs) 90, 92, 95
wireless 96
logical operators
in queries 59
in spreadsheets 162–3
logon and logoff procedures 97–8
machine-centred systems 8, 214
macros 156, 170
magnetic ink character recognition (MICR)
134–5
magnetic tape 55, 130
mail sorting 195
maintenance, system 30–1
management
data 148, 149
dialogue 148, 149
model 148, 149
management information systems (MISs) 38, 138
managers 30
manual transaction systems 118
manufacturing 187
mass production 207
media
and multimedia design 236
types of 220–2
merging technologies 255–6
messaging systems 81–6, 104
metadata 47
microphones 247
microwave transmission 95–6
MIDI (Musical Instrument Digital Interface) 252
mobile phones 96
model management 148, 149
mono 224
morphing 227
motion sensors 201
MPEG (Motion Picture Expert Group) 252
MP3 (MPEG Audio Layer 3) 252
multimedia systems
animation processing 227–8
audio storage 224–6
characteristics 220–8
defined 220
design 235–6
displaying in 238–44
education and training 230
encyclopaedia 231
examples 230–6
hardware 238–40
image storage 223–4
and information 231–2
and interactivity 222
leisure and entertainment 230
major areas of use 230–3
and mode of display 222
and people 228
and print 222
and technology advances 233–5
and text 220, 236
video processing 226–7
virtual reality and simulations 232–3
negotiation skills 6
network
access methods 92
administrator 96
hardware 92–6
software 96–8
topologies 91–2
network interface card (NIC) 93
network operating systems (NOS) 96–7
networks 89–91
local area (LANs) 90, 92, 95, 96
neural 157–8, 175
wide area (WANs) 90
neural networks 157–8, 175
node 49, 89
noise 211
non-computer
organisational methods 42–3
procedures 140
normalisation 48–9
numbers 220–1
numerical control (NC) 194
office automation systems 38
offline storage 55
online storage 55
operating systems 96–7
operation manual 31
operators
in queries 58–9
in spreadsheets 162–3
optical disc 55
organisation methods 42–52
organisational feasibility 16
organising a multimedia product 247–8
OSI reference model 77
packet switching 90
parallel
conversion 27
transmission 87
parameter 79
parity 79
checking 78
participant
development 18–20
training 27
Index
271
passwords 97
path-based animation 227
people
in multimedia systems 228
as participants 140
phased conversion 27
photodiode 202
PICT (Picture) 251
pie charts 174
pilot conversion 28
pivot table 172
pixel 221
point-of-sale terminals 122
presentation software 241
presentations, on-screen 241
primary
data 176
key 44
print
and interactivity 222
and mode of display 222
and multimedia 222
privacy 70, 104, 181, 255
private leased line 90
processing data 100–2, 188, 207–8, 248
production
assembly line 192–3
batch system 208
continuous systems 208
discrete system 208
mass 107
programmable logic controllers (PLCs) 192
programmers 6
project
goal 4
leader 6
management 4
management software 4, 242
manager 228
plan 4–5, 17
projection devices 239–40
protocols 77, 88–9
prototypes 13–14
query by example (QBE) 57
query language 59
querying 57
QuickTime 252
radio and Internet 107
range 154
check 69
raster scan 239
RealAudio file format 252
real-time transaction processing 115–17, 120–3,
132–3
see also batch transaction processing
receiver 76
record 43
recovery process 129
refreshing 239
relational
databases 44–6
272
Index
operators 58
relationship 44
relative referencing 163–4
relay 210
removable cartridge 55
reporting 64–5
reports 172
analysis report 17
requirement 13
requirement report 13
reservation systems 120–1
resistance thermometers 200
resolution 221
retrieval, data 53–62, 126–33, 178, 249–53
RTF (Rich Text Format) 250
ring topology 92
routers 93
safety, workplace 215
sample size 224
sampling rate 224
satellites 96
scanners 245
schedule feasibility 16
schema 44–6
schematic diagrams 48
screen 222, 238–9
layout 236
script 247
search
engines 60–2, 172
robot 62
searching 57–62
secondary
data 176
key 44
security, data 56, 141–2
semi-automation 214
sensors 188, 199–202
flow 201
light 201–2
motion 201
pressure 200–1
temperature 200
sequential access 54, 130, 131
serial transmission 87, 88
servers 93
shielding 211
signal 211
signal conditioning 211
simplex mode 88
simulations 232–3
simulators, flight 233
single key 44
skills
communication 6
negotiation 6
social design 8–12
software animation 243
application 241–2
audio 242
authoring 242
flow control 77
graphics 242
information management 4
multimedia 240–4
network 96–8
presentation 241
project management 4, 242
video 242
solenoids 209
solutions, designing 18–25
sorting 56–7
sound card 247
speakers 222, 240
speed of transmission 77–8
spreadsheets
analysis 172–4
defined 154–6
designing 160–4
functions operators 162
SQL 59–60
star topology 91
statistical analysis 173
stepper motors 209–10
stereo 224
stock prices 153
storage
data 53–62, 126–33, 178, 249–53
media 55
offline 55
online 55
storyboard 50–1, 247–8
structured data 176
Structured Query Language (SQL) 59–60
switches 93
symmetric encryption 55
synchronous transmission 87, 88
system
defined 190
designer 228
evaluation 30
flowcharts 24–5
maintenance 31
testing 28, 30
system development cycle 3, 30
systems
analysts 6
automated manufacturing 187–95, 198–205,
208–11, 213–15
communication 76–86, 104–8
and ethics 10–12
expert 37, 156–7, 167–8, 175, 177
human-centred 8
intelligent 179–80
machine-centred 8
messaging 81–6, 104
multimedia 220–8, 230–6, 238–43, 245–57
reservation 120–1
transaction processing 37, 113–18, 119–25,
130–1, 134, 139–42
see also decision support systems
tables 46
team building 6
technical
feasibility 16
staff 228
support staff 27
technologies, merging 255–6
telecommuting 107
teleconferencing 81
telephone 81, 103
temperature sensors 200
templates 155, 160
terminals 89
test data 28
testing, system 28
text
colour 236
file formats 250
and multimedia 220, 236
thermistor 200
thermocouples 200
TIFF (Tagged Image File Format) 251
titling 236
token ring 92
top-down design 18
touch screens 239
training and multimedia 230
transaction processing monitor (TP monitor) 116
transaction processing systems (TPSs) 37, 113–18,
119–25, 130–4, 139–42
transducers 199
transition 241
transmission
of data 87–98, 211–12
media 76, 94–6
microwave 95–6
speed 77–8
wire 94–5
wireless 95
transmitter 76
tuple 46
TWAIN (Technology Without An Interesting
Name) 245
tweening 227
twisted-pair cable 95
two-phase commit 55
type check 69
uniform resource locator (URL) 49–50
unstructured data 176, 180
user interface 161
user-friendly 8–9
validation of data 69, 117
VCR (video cassette recorder) 246
vector
display systems 239
graphics 221
video 236
cameras 246
capture 226
capture card 246
conference 81
defined 222
file formats 252
Index
273
and Internet 107
live 255
processing 226–7
software 242
virtual reality (VR) 232–3
voice mail 82
warping 228
WAV file format 251
Web
browsers 243
site 233
what-if models 154, 172–3
wide area networks (WANs) 90
wildcard characters 58
wire transmission 94–5
WMF (Windows Metafile Format) 251
work
environment 9–10
nature of 10, 139–40, 213
working from home 107–8
workplace safety 215
workstations 90
World Wide Web (WWW) 49, 233–4
Acknowledgments
The publisher wishes to thank Catherine Webber, Rick Walker and Anthony Connolly for their assistance
with this project.
The author and publisher would like to thank the following for granting permission to reproduce the
copyright material in this book:
The Age, pp. 246 (bottom), 252; Coo-ee Picture Library, p. 96; Corbis/Australian Picture Library, p. 117;
Malcolm Cross, pp. 28, 76, 77, 130, 177, 234, 240, 247; Randy Glasbergen, p. 102; Great Southern
Stock/Brian Gilkes, p. 123, 150 (centre); The Image Bank, p. 193; Mark Parisi, pp. 31, 56, 141, 182, 195,
232; PhotoDisc, pp. 7, 17, 27, 30, 38, 42, 81, 90, 107, 135, 140, 148 (all), 150 (right and left), 152, 160,
199, 202; Redflex Systems, p. 232 (top); Ellen Sheerin, pp. 227, 228; Yurikamome, p. 179.
Every effort has been made to trace and acknowledge copyright. The author and publisher would
welcome any information from people who believe they own copyright to material in this book.
274
Index
175P IPT HSC Cover
7/9/00 9:13 AM
Page 1
Key features
• list of outcomes and overview at the beginning of
each chapter
• social and ethical issues and Internet activities integrated
throughout the book
• numerous practical tasks that can be used with any
software or make of computer
• case studies and examples of information systems
• learning activities to help students apply the content in
every section
• chapter review at the end of each chapter
• interesting IT facts and cartoons 1to2promote
3 4 5class
67890-1234567890-1234567890discussion
QWERTYUYIOPQWERTYUYIOPQWERTYUYIOP
• key terms highlighted for quick reference
• glossary
• index.
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567890-1234567890UYIOPQWERTYUYIOP
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Additional resources to support and
are0 - 1 2 3 4
1 2extend
3 4 5this
6 book
789
available at Heinemann’s World Wide Web site, hi.com.au.
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These include a sample teaching program, assessment
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advice and answers to exercises from AtheS textbook.
About the author
Greg Powers is a head teacher with many years’ experience
in writing and implementing computing studies programs.
He is the author of several highly successful texts including
Computing Studies–An Introductory Course.
ISBN 0 86462 501 4
ISBN 0-86462-512-X
You can visit the Heinemann World Wide Web site at
hi.com.au or send email to info@hi.com.au
9 780864 625120
G.K. Powers
Also available
Preliminary Course
Heinemann Information Processes and Technology: HSC Course
HSC Course has been written to meet all of the
requirements of the new Information Processes and
Technology syllabus in NSW. This text will help students to
develop their understanding of information processes in the
context of different information systems. It is designed to
build on the knowledge and skills gained in the Preliminary
course and to help students become confident, competent,
discriminating and ethical users of information technology.
This text provides up-to-date information, a practical
approach, and a large number of questions that cater for a
wide range of students.
H e i n e m a n n
and Technology
HSC COURSE
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G. K. Powers

Here - Warilla High School Intranet

Transcription

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