Engineering Semantic Web Information Systems

1. Engineering Semantic Web Information Systems Richard Vdovjak Flavius Frasincar Geert-Jan Houben Peter Barna Databases & Hypermedia Group Department of Computer Science /dept. of mathematics and computer science wwwis.win.tue.nl/~hera PACIS'03

2. Overview • Motivating example: Virtual art gallery • Hera framework, models and technologies • Hera Back-end: Integration engine • Hera front-end: Presentation generation engine • Summary and future work PACIS'03

3. Virtual art gallery WIS • Create “on-the-fly” exhibitions • painters, paintings, techniques... • Many to many content delivery • Triggered by the user query • Exhibits (Images) are from (online) Art catalogues • Descriptions are gathered from an (online) Art Encyclopedia PACIS'03

4. We need a framework that offers • Semantics • Express concepts and their hierarchies • Relationships among the concepts • Query language that can exploit the above • Access to several sources • Flexible source management • Flexible query mediation • User/platform adaptation • (adaptability and adaptivity) • Automated presentation design • Based on the user query, • Device profiles and the browsing history PACIS'03

5. The Hera Framework: Design Steps, Models, and Processing Engines PACIS'03

6. Conceptual Model Presentation Engine Integration Engine Overview of the System PACIS'03

7. Conceptual Model (CM) • Provides a uniform semantic view over different data sources that are integrated within a given Web application • Consists of hierarchies of concepts relevant within the given domain, their properties, and relations • Encoded in RDF(S) PACIS'03

8. RDF(S), RQL • RDF(S) • W3C standard for describing metadata • Directed labeled graph formalism • Formal semantics defined • RQL: select X from {X:Technique}tname{Xtname} where Xtname = "Chiaroscuro" PACIS'03

9. Conceptual Model Example PACIS'03

10. Source Clusters Sources are • Autonomous • (Virtually) grouped to clusters based on the content they provide • RDF(S), RQL capable PACIS'03

11. Integration Model IM decouples the CM and Sources • Articulations • actual links between the CM and the source ontologies • concept/instance uniqueness • (a part of it) serves as a query on the source side • Decorations • offer a way to rank sources within the same cluster • capture explicitly designer’s knowledge about sources • the order in which the sources are consulted is flexible • open possibilities for queries with constraints e.g. “I’m interested in the answer within 1 s, otherwise forget it” PACIS'03

12. Integration Model Ontology • Path expression • Primary node (including its ID) • Sequence of nodes and edges • Articulation • Target and Source path expressions • Decoration • Value based ordering criterion • e.g. ResponseTime, Reliability • Processing instruction • Transformers (e.g. Literal2String) Application independent PACIS'03

13. Integration Model Instance:Articulation Example Target Path Expression cm:aname idByValue ends follow starts cm:Painting cm:picture Image pe_to3 target a2_1 obtainedFrom obtainedFrom follow endsL source starts ac:Painting ac:visualized URL pe_from3 applies transformedBy srcAddress idByValue URL2ImageTransf http://www…ac ac:title Source Path Expression (query for the source) d2_1 0.9 Decoration (Reliability) PACIS'03

14. Source Management Front-end Back-end Conceptual Model Access Point User Query Integration Model html/smil IM Instance Presentation IM Specialization Sources PACIS'03

15. Query answering • Query mediation • For every variable in the query find articulations in the IM instance pool • If there more articulations for one variable sort them based on the chosen decoration(s) • Execute the “source” path expression queries at the the sources • Perform the required processing instruction/data transformations • Assemble the results PACIS'03

16. Application Model (AM) • AM serves as a presentation blue-print • Describes hypermedia aspects of the presentation. • Captures the navigational view over the CM • Consists of (nested) slices and slice relationships • Slices - meaningful presentation units • Associated to concepts from the CM • Contain properties and possibly other slices (nesting) • Slice relationships: • Aggregation relationships: index, tour, indexed guided tour… • Reference relationships: link with an anchor specified. • Encoded in RDF(S). PACIS'03

17. Application Model Example PACIS'03

18. Adaptation/User Model • Captures two kinds of adaptation • Adaptability takes into account the situation in which the user will use the presentation (e.g. the browsing platform). • Adaptivity means that the presentation changes itself according to the “state of the user’s mind” while being browsed. • Consists of • Device/User Profile captures “static” visual and platform preferences encoded in CC/PP. • User Session represents the dynamic user’s state, e.g. did the user visit (learn) this slice (concept). • Application and Update Rules describe the behaviorof the presentation (e.g. conditional slices in AM) and keep the User Session up-to-date (AHAM rules). PACIS'03

19. Adaptation Model Example PACIS'03

20. Adaptation Model Syntax • Adaptability Condition • Adaptivity Condition <rdfs:Class rdf:ID=“Slice.painting.picture” slice:condition=“prf:ImageCapable=Yes”> <rdf:subClassOf rdf:resource=“#Slice”/> </rdfs:Class> <rdfs:Class rdf:ID=“Slice.painter.main” slice:condition=“um:Technique < 10”> <rdf:subClassOf rdf:resource=“#Slice”/> </rdfs:Class> PACIS'03

21. Profile Example • Device/User Profile (CC/PP encoding) Screen size: 100x80, preferred language: English <rdf:Description rdf:about=“Profile”> <ccpp:component> <prf:HardwarePlatform> <prf:ImageCapable>No</prf:ImageCapable> <prf:ScreenSize>100x80</prf:ScreenSize> … </prf:HardwarePlatform> </ccpp:component> <ccpp:component> <up:UserPreferences> <up:Language>English</up:Language> … </up:UserPreferences> </ccpp:component> </rdf:Description> PACIS'03

22. Rendering • XSLT code generation • Different code generators: • HTML for PC Web browsers • SMIL code for multimedia presentations • WML code for WAP phone browsers WML XSL HTML XSL <xsl:template match=“slice-instance”> <TABLE> <xsl:apply-templates select=“*”/> </TABLE> </xsl:template> <xsl:template match=“slice-instance”> <CARD id=“{@id}”> <xsl:apply-templates select=“*”/> </CARD> </xsl:template> PACIS'03

23. Resulting Hypermedia Presentations HTML WML SMIL PACIS'03

24. EROS: exploring the CM • Explorer for RDFS-based OntologieS • multiple views over the same model • support for RQL queries construction PACIS'03

25. Summary Hera: CM in RDF, RDFS • Semantics • Express concepts and their hierarchies • Relationships among the concepts • Query language that can exploit the above • Access to several sources • Flexible source management • Flexible query mediation • User/platform adaptation • (adaptability and adaptivity) • Automated presentation design • Based on the user query, • Device profiles and the browsing history RQL IM Articulations IM Decorations UM, U/P Profile (CC/PP) AM in RDF, RDFS PACIS'03

26. Present & Future Work • Applying our approach in different domains • Virtual museum • Photo Portal • Medical science (drug/disease ontologies) • Optimization issues • Authoring tools for the underlying models • Initial correlation for Schema Integration PACIS'03