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An Engine for Generating XSLT from Examples
An Engine for Generating XSLT from Examples José Paulo Leal | Ricardo Queirós CRACS & INESC-Porto LA Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre, 1021 4169-007 Porto PORTUGAL Outline Introduction Related work The Vishnu engine 1. 2. 3. Validation 4. 5. Architecture Context Generation Refinement consistency (unit testing) coverage of the existing rules (scenarios) adequacy (GWT web application) Conclusions and future work 1. Introduction Extensible Stylesheet Language Transformations (XSLT) powerful & widely used language for transforming XML documents overwhelming for novice or infrequent users XSLT program inference from examples, based on source and target documents. seldom adequate for production usage … … but can be used as a skeleton of the final program as scaffolding in the process of coding it 2. Related work Environments for programming in XSLT XSLT editors Environments Types IDE XML IDE’s General purpose IDE’s Independent/Standalone Examples Altova StyleVision, Stylus Studio, oXygen TigerXSL, XSL Tools, OrangeVoltXSLT, X-Assist Dexter-xsl, VXT, FOA XSLT generators Example-based annotation tool Annotation-based page-clipping engine 3. The Vishnu engine Vishnu - Visual programming tool for creating XSLT programs Composed by 2 components Programming engine (server) automatic generation of XSLT program from examples using 2nd order transformations Graphical Editor (client) - user interaction where the programmer loads and edits document examples pairs their content using graphical primitives 3. The Vishnu engine Vishnu - Generation pairs <vishnu xmlns="http://www.dcc.fc.up.pt/vishnu"> <source>...</source> <target>...</target> <pairings> <pairing source = "/rss[1]/channel[1]/title[1]/text()” target = "/html[1]/head[1]/title[1]/text()"/> <pairing source = "/rss[1]/channel[1]/title[1]/text()” target = "/html[1]/body[1]/h1[1]/text()"/> </pairings> </vishnu> generates <xsl:template match="/"> <html><head>title> <xsl:value-of select="/vishnu/source/rss[1]/channel[1]/title[1]/text()"/> </title></head><body><h1> <xsl:value-of select="/vishnu/source/rss[1]/channel[1]/title[1]/text()"/> </h1></body></html> </xsl:template> 3. The Vishnu engine Vishnu communication between components is regulated by the Vishnu API the Vishnu façade class implements the Vishnu API hides the inner structure of the XSLT generator organized in three main components context generator refiner 3. The Vishnu engine Vishnu XML – Context (1) file with data for the generation process Formalized by the following XML Schema: source: a copy of the source document target:: a copy of the target document pairings: list of pairing relating the two documents <pairing source="/rss[1]/channel[1]/title[1]/text()” target="/html[1]/head[1]/title[1]/text()"/> 3. The Vishnu engine Vishnu – Context (2) converts text into XML and vice-versa converts text locations (offsets) into IdPaths expressions and vice-versa IdPath is an absolute XPath expression which selects either single texts or attribute nodes in an XML document: /n1[p1]/.../nn[pn]/text() /n1[p1]/.../nn[pn]/@attr 3. The Vishnu engine Vishnu – Generation (1) produces an initial XSLT program from source, target and mapping a default mapping the Is inferred if no mapping is provided by the client links text or attribute nodes in both documents (equal character strings) initial XSLT program has a single template containing an abstraction of the target document target positions in the mapping are replaced with xsl:value-of instructions processes documents with the same structure of the source document a refinement process abstracts this program 3. The Vishnu engine Vishnu – Refinement (1) Produce a high quality XSLT program from the initial program Composed by a set of 2nd order transformations (refinements) Control of the refinement process Based on strategies (process sequencing) Implemented in Java Two types of refinements: Simplifications Abstractions 3. The Vishnu engine Vishnu Two – Refinement (2) types of refinements: Simplifications: Preserve the program semantics, changing its syntax Improve the readability of XPath expressions and extract global variables Examples: Context, Melt, Extract and Join Abstractions: Change both the syntax and semantics of the program Generalize templates and restructure large templates in several smaller ones Examples: Generalize and Structure 4. Validation The 1. 2. 3. Vishnu engine was validated in 3 approaches: consistency of the generation and refinement process; coverage of the existing rules; adequacy of the Vishnu API to XSLT editing environments 4. Validation Consistency 1. Validation of the consistency of the generation and refinement process by checking that each intermediate transformation converts the example source document into the examples target document. If this invariant is not satisfied then the refinement process is aborted and an error is reported to the client. 4. Validation Coverage 2. based on scenarios each scenario includes source and target document and a mapping, as well as the expected program for each scenario the generated output of the engine is matched with the resources enclosed on the scenario itself current scenarios include the conversion of: RSS documents to HTML Mathematical expressions in MathML to presentation MathML Meta-data in LOM (Learning Object Metadata) to RDF 4. Validation Adequacy 3. To validate the adequacy of the Vishnu API we developed a simple web environment for XSLT programming based on the Google Web Toolkit (GWT) Conclusion and future work Conclusion Design of Vishnu a visual XSLT programming tool Based on examples Produces a high-quality XSLT based on a set of refinements Project in implementation phase (client) Future work Editor Improve web interface IDE integration Engine Support refactoring features Support mixed-content Questions? Authors José Paulo Leal zp@dcc.fc.up.pt http://www.dcc.fc.up.pt/~zp Ricardo Queirós ricardo.queiros@eu.ipp.pt http://www.eseig.ipp.pt/docentes/raq Thanks!
