1. Semantic Web and Its Applications Ching-Long Yeh 葉慶隆 Department of Computer Science and Engineering Tatung University Taipei, Taiwan Email: chingyeh@cse.ttu.edu.tw http://www.cse.ttu.edu.tw/chingyeh

2. Web Technology Evolution

3. SW & Applications3 Web Technology HTML XML Electronic Business Semantic Web

4. SW & Applications4 Information Pool WWW HTTP (Hyper Text Transport Protocol) HTML (Hyper Text Markup Language) URL (Uniform Resource Locator) Web server Application Client HTTP URL HTML Document Human-to-machine interaction Information explosion

5. SW & Applications5 Information Pool Interaction Using XML XML (eXtensible Markup Language) SOAP (Simple Object Access Protocol) SOAP server Application HTTP XML Document Machine-to-machine interaction Service automation SOAP server Application Information Pool XML Document

6. SW & Applications6 Web Service Architecture

7. SW & Applications7 Electronic Business Transport, routing, packaging Business processes, business documents Company A Company B Transport, routing, packaging Business processes, business documents ERP Application-to-Application Business Process Automation RosettaNet ebXML

8. SW & Applications8 Semantic Web The Semantic Web is a vision: See “W3C Semantic Web Activity,” by Marja-Riitta Koivunen, for more descriptions.W3C Semantic Web Activity the idea of having data on the web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications

9. SW & Applications9 Semantic Web The Semantic Web is the new generation of the World Wide Web, based on the semantic network knowledge representation formalism, which enables packaging information in the form of object-attribute-value statements, so called triples. By assuming that terms used in these statements are based on the formally specified meaning (for the community of interest), i.e. ontologies, these triplets can be semantically processed by machine agents. From: http://www2002.org/CDROM/poster/130.pdf

10. SW & Applications10 The Semantic Web Layered Architecture (http://www.w3.org/2001/T alks/0228-tbl/slide5-0.html) Tim Berners-Lee: “Axioms, Architecture and Aspirations” W3C all-working group plenary Meeting 28 February 2001 URIUnicode XMLNamespaces XML Schema Sig RDF M&S RDF Schema Ontology Rules Logic Proof Trust

11. SW & Applications11 A Metadata Layer View of the SW Resources on the WWW Metadata layer upon the WWW Schema in OWL Instances in RDF

12. Semantic Web Languages

13. SW & Applications13 What is XML? Extensible Markup Language A Syntax for Documents A Meta-Markup Language A Structural and Semantic Language, not a Formatting Language Not just for Web pages

14. SW & Applications14 XML Standards DTD Namespace Schema DOM CSS, XSL-T, XSL-FO XLink XPointer

15. SW & Applications15 XML Protocol: SOAP

16. SW & Applications16 RDF M&S RDF (Resource Description Framework) –Beyond Machine readable to Machine understandable RDF consists of two parts –RDF Model (a set of triples) –RDF Syntax (different XML serialization syntaxes) RDF Schema for definition of Vocabularies (simple Ontologies) for RDF (and in RDF)

17. SW & Applications17 RDF Data Model Resources –A resource is a thing you talk about (can reference) –Resources have URI’s –RDF definitions are themselves Resources (linkage, see requirement 1) Properties –slots, define relationships to other resources or atomic values Statements –“ Resource has Property with Value ” –(Values can be resources or atomic XML data) Similar to Frame Systems

18. SW & Applications18 A Simple Example Statement –“Ora Lassila is the creator of the resource http://www.w3.org/Home/Lassila ” Structure –Resource(subject) http://www.w3.org/Home/Lassila –Property(predicate) http://www.schema.org/#Creator –Value(object) "Ora Lassila” Directed graph http://www.w3.org/Home/Lassila s:Creator Ora Lassila

19. SW & Applications19 EmailName s:Creator http://www.w3.org/Home/Lassila Another Example To add properties to Creator, point through an intermediate Resource. Person://fi/654645635 Ora Lassila lassila@w3.org

20. SW & Applications20 Example: Bag The students in course 6.001 are Amy, Tim, John, Mary, and Sue Rdf:Bag /Students/Amy /Students/Tim /Students/John /Students/Mary /Students/Sue bagid1 /courses/6.001 students rdf:type rdf:_1 rdf:_2 rdf:_3 rdf:_4 rdf:_5

21. SW & Applications21 rdf:_1 rdf:_2 rdf:_3 rdf:type source ftp.eu.net ftp.cs.purdue.edu ftp.x.org Example: Alternative The source code for X11 may be found at ftp.x.org, ftp.cs.purdue.edu, or ftp.eu.net altid rdf:Alt http://x.org/package/X11

22. SW & Applications22 RDF Schema (RDFS) RDF just defines the data model Need for definition of vocabularies for the data model - an Ontology Language! The RDF Schema mechanism provides a basic type system for use in RDF models. The RDF schema specification language is less expressive, but much simpler to implement, than full predicate calculus languages such as CycL and KIF.

23. SW & Applications23 Most Important Modeling Primitives Core Classes –Root-Class rdfs:Resource –MetaClass rdfs:Class –Literals rdfs:Literal rdfs:subclassOf -property Inherited from RDF: properties (slots) rdfs:domain & rdfs:range rdfs:label, rdfs:comment, etc. Inherited from RDF: InstanceOf ( rdf:type )

24. SW & Applications24 OWL W3C Web Ontology Language OWL provides three increasingly expressive sublanguages: OWL Lite, OWL DL, and OWL Full.

25. SW & Applications25 OWL W3C Web Ontology Language OWL Lite language constructs RDF Schema Features: Class rdf:Property rdfs:subClassOf rdfs:subPropertyOf rdfs:domain rdfs:range Individual (In)Equality: equivalentClass equivalentProperty sameAs differentFrom allDifferent Property Characteristics: inverseOf TransitiveProperty SymmetricProperty FunctionalProperty InverseFunctionalProperty Property Type Restrictions: allValuesFrom someValuesFrom Restricted Cardinality: minCardinality (only 0 or 1) maxCardinality (only 0 or 1) cardinality (only 0 or 1) Header Information: ontology imports

26. SW & Applications26 The Big Picture of SW (http://semanticweb.org/about.html#bigpicture)

27. SW & Applications27 Uses Cases of Web Ontologies Web portal Multimedia collections Corporate web site management Design documentation Agents and services Ubiquitous computing

28. SW & Applications28 An Architecture of An Architecture of Semantic Community Web Portals (From: http://www9.org/w9cdrom/134/134.html)

29. Sesame A generic Architecture for Storing and Querying RDF and RDF Schema

30. SW & Applications30 What is Sesame ? Sesame is RDF Schema-based repository and querying facility that offers: –persistent storage of RDF data –export of repository contents in RDF format –data administration functionality –query engine (RQL, SeRQL)

31. SW & Applications31 Sesame’s Architecture

32. SW & Applications32 The RQL Query Module The Query Module follows the path when handling a query.

33. SW & Applications33 The Admin Module Two main functions : –Incrementally adding RDF data/schema information. –Clearing a repository. The Parser delivers the information to the admin module on a per- statement basis : (S, P, O). The admin subsequently checks each statement for consistency with the information already present in the repository, and infers implied information if necessary, as follow:

34. SW & Applications34 The Admin Module(2) If P equals type, then the admin infers that O must be a class. If P equals subClassOf, then the admin infers that both S and O are classes. If P equals subPropertyOf, then admin infers that both S and O are properties. If P equals domain or range, the admin infers that S must be a property and O must be a class.

35. SW & Applications35 The RDF Export Module Exports data in RDF format -Output contains actual contents of repository, query engine outputs query results

36. SW & Applications36 RQL (RDF Query Language) Based on OQL (standard QL for object-relational DBMS) –Set of core queries Class, Property, subClassOf, … –Filters Select-from-where –Boolean expressions –Functional composition of queries Path expressions –For navigating the RDF model –Allowing bridging between RDF data and schema information

37. KA2 An Ontology-Based Community Web Portal

38. SW & Applications38 KA2 Knowledge Annotation Initiative of the Knowledge Acquisition Community The basic scenario –WWW documents of the KS community were annotated according to the schema of an ontology. –The annotations enable intelligent access to these documents and infer implicit knowledge from explicitly stated facts and rules from the ontology.

39. The KA2 Ontology Class hierarchy Person Employee Academic-Staff Lecturer Researcher Administrative-Staff Secretary Technical-Staff Student Phd-Student Relations Address, Affiliation, Cooperates-With, Editor-Of,Email, First-Name, Has- Publication, Head-Of-Group, Head-Of- Project, Last-Name, Member-Of- Organization, Member-Of-Program- Committee, Member-Of-Research-Group, Middle-Initial, Organizer-Of-Chair-Of, Person-Name, Photo, Research-Interest, Secretary-Of, Studies-At, Supervises, Supervisor, Works-At-Project Person-ontology Class hierarchy On-Line-Publication Publication Article Article-In-Book Conference-Paper Journal-Article Technical-Report Workshop-Paper Book Journal IEEE-Expert IJHCS Special-Issue Relations Abstract, Book-Editor, Conference- Proceedings-Title, Contains-Article-In- Book, Contains-Article-In-Journal, Describes-Project, First-Page, Has- Author, Has-Publisher, In-Book, In- Conference, In-Journal, In-Organization, In-Workshop, Journal-Editor, Journal- Number, Journal-Publisher, Journal-Year, Last-Page, On-Line-Version, … Publication-ontology

40. SW & Applications40 Accessing the Community Web Portal Query capability –In F-Logic mechanism Navigating capability –As the easy-to-use front-end of the query mechanism

43. SW & Applications43 Providing Information Integrating various syntactic and semantic formats based on the common ontology Three different modes of information provision are supported –Metadata-based information –Wrapper-based information –Fact-based information

44. SW & Applications44 Development of Web Portals

45. SW & Applications45 Summary Semantic Web technology –Metadata –Facilitate interoperability at semantic level –Relieve the problem of information explosion –Enable the knowledge management