A Survey of Issues and Approaches in Automatic Service Composition

A Survey of Issues and Approaches in Automatic Service Composition

A Survey of
Issues and Approaches in
Automatic Service Composition
Ulrich Küster1 Mirco Stern2 Birgitta König-Ries1
1
Institute of Computer Science, Friedrich-Schiller-Universität Jena,
ukuester | koenig@informatik.uni-jena.de
2 Institute for Program Structures and Data Organization, Universität
Karlsruhe, mirco.stern@stud.uni-karlsruhe.de
Vision
Why does automatic service composition
get that much attention?
Automatic service composition might
enable programming to become
specifying what to do and
not anymore how to do it!
Ulrich Küster - FSU Jena
WESC05 12.12.2005
2
Envisioned Use Case
(Mobile) Application
Program
Logic
Service
Request
Program
Logic
useService
Service Oriented Middleware
Network
(Internet, Cell-based, Ad-hoc, …)
Service
Provider
Ulrich Küster - FSU Jena
Service
Provider
Service
Provider
WESC05 12.12.2005
Service
Provider
Service
Provider
3
A (trivial?) example
(Mobile)
Application
No such service
available…
Service Request:
Service
Desc
pdf
printer
Ulrich Küster - FSU Jena
Print MS Word - Document
Service
Desc
Service
Desc
Service
Desc
Service
Desc
.doc to .pdf
converter
.doc to .ps
converter
ps
printer
spell
checker
WESC05 12.12.2005
4
An obvious solution
(Mobile)
Application
Service Request:
Print MS Word - Document
Service
Desc
.doc pdf
to .pdf
converter
printer
Ulrich Küster - FSU Jena
Service
Service
Desc
Desc
pdfto .pdf
.doc
printer
converter
Service
Desc
Service
Desc
Service
Desc
.doc to .ps
converter
ps
printer
spell
checker
WESC05 12.12.2005
5
An obvious solution
(Mobile)
Application
A suitable
composition
Service
Desc
Service
Desc
☺
Service
Desc
.doc printer
pdf
.doc to .pdf
(.doc to .pdf converter
printerpdf printer)
converter
Ulrich Küster - FSU Jena
Service Request:
Print MS Word - Document
Service
Desc
Service
Desc
Service
Desc
.doc to .ps
converter
ps
printer
spell
checker
WESC05 12.12.2005
6
Fulfilling Preconditions
• Problem: requested effect available, but
service's preconditions not met
• Solution: chaining of services
• Many implementations
– graph search
– forward chaining
– backward chaining
– estimated regression planning
Ulrich Küster - FSU Jena
WESC05 12.12.2005
7
Problems
• Scalability
– exploit special characteristics of search space
• Degrading quality in long service chains
– transformation processes
– probability of failure
• Determining acceptable side-effects
Ulrich Küster - FSU Jena
WESC05 12.12.2005
8
Another example
(Mobile)
Application
Service Request:
No such service
available
Vacation somewhere in Italy,
booking of hotel and flight to
nearby airport
Service
Desc
Traveltopia
Ulrich Küster - FSU Jena
Service
Desc
Service
Desc
Service
Desc
eFlights
Opodo
eHotel
WESC05 12.12.2005
Service
Desc
ItalianHotels
9
Generating Multiple Effects
(Mobile)
Application
(Mobile)
Application
Service Request:
Service Request:
Service Request:
☺
Service
Service
DescDesc
Traveltopia
Traveltopia
Ulrich Küster - FSU Jena
Flight to Italy
Hotel in Italy
Vacation somewhere in Italy,
booking of hotel and flight to
nearby airport
Applicable services
exist, but must be
coordinated
Service
Service
DescDesc
Service
Service
DescDesc
Service
Service
DescDesc
eFlights
eFlights
Opodo
Opodo
eHotel
eHotel
WESC05 12.12.2005
☺
Service
Service
DescDesc
ItalianHotels
ItalianHotels
10
Generating Multiple Effects
• Problem: Decompose request, coordinate
several services
• Many approaches that differ in degree of
automation
– Behavior-Based Composition
– Component-Based Composition
Ulrich Küster - FSU Jena
WESC05 12.12.2005
11
Problems
• Central Problems:
– Scalability
– Transactional properties
– Balancing amount of information in the
service request
• Quantified Requests
– Important (but so far ignored?) special case
Ulrich Küster - FSU Jena
WESC05 12.12.2005
12
Yet another example
(Mobile)
Application
Service Request:
Hotel in Amsterdam (< 100 €),
close to public transportation to
central station and Mercure Hotel
Hotelbookings available, but
need to know price and location…
Service
Desc
hotels.com
Ulrich Küster - FSU Jena
WESC05 12.12.2005
Service
Desc
Service
Desc
hotels.nl
bookings.nl
13
Missing knowledge
(Mobile)
Application
Service Request:
Hotel in Amsterdam (< 100 €),
close to public transportation to
central station and Mercure Hotel
☺
Check price and location first …
reserve hotel afterwards…
1
Service
Desc
Price-check
Ulrich Küster - FSU Jena
Service
Desc
public
transportation
guide service
Service
Desc
hotels.com
WESC05 12.12.2005
☺
2
Service
Desc
Service
Desc
hotels.nl
bookings.nl
14
Missing Knowledge
• Problem: Need to acquire missing
knowledge
• Solution: Additional knowledge gathering
services
• Two options:
– Knowledge gathering while searching
– Conditional plans
Ulrich Küster - FSU Jena
WESC05 12.12.2005
15
Problems
• Knowledge gathering while searching
– world-altering effects (cost)
– life span of knowledge
• Conditional plans
– unrealistically high number of paths
• Generally difficult to determine whether
and which knowledge is missing
Ulrich Küster - FSU Jena
WESC05 12.12.2005
16
Summary and Conclusion
• Three (orthogonal) classes of composition
problems:
– fulfilling preconditions
– generating multiple effects
– missing knowledge
• Classified existing solutions
– sole focus on automatic composition synthesis
• Discussed main problems
Ulrich Küster - FSU Jena
WESC05 12.12.2005
17
Thank you!
Are there any questions?
Further information: http://hnsp.inf-bb.uni-jena.de/diane/