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Introduction to Semantic Web Portal

Introduction to Semantic Web Portal. Ching-Long Yeh 葉慶隆 Department of Computer Science and Engineering Tatung University chingyeh@cse.ttu.edu.tw http://www.cse.ttu.edu.tw/chingyeh. Content. Background XML, XML Protocol and Web Services EB Standard: RosettaNet EB Standard: ebXML

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Introduction to Semantic Web Portal

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  1. Introduction to Semantic Web Portal Ching-Long Yeh 葉慶隆 Department of Computer Science and Engineering Tatung University chingyeh@cse.ttu.edu.tw http://www.cse.ttu.edu.tw/chingyeh

  2. Content • Background • XML, XML Protocol and Web Services • EB Standard: RosettaNet • EB Standard: ebXML • Semantic Web: Machine Processable Web • Ontology Basics • XML-based Ontology Languages: RDFS, DAML, OWL • DAML-S: an Ontology for Semantic Web Services • Semantic Web Portals • Conclusions EB & SWS

  3. Background • WWW • HTML • HTTP • Mainly man-machine interaction • Electronic Business (EB) • Standard XML document • XML Protocol • AP-2-AP interaction • Semantic Web Services • RDF • Ontology • Web Services, agents EB & SWS

  4. 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 EB & SWS

  5. XML Standards • DTD • Namespace • Schema • DOM • CSS, XSL-T, XSL-FO • XLink • XPointer EB & SWS

  6. XML Protocol: SOAP EB & SWS

  7. <?xml version=“1.0” encoding=“UTF-8”?> <SOAP:Encelope xmlns:SOAP=http://schemas.xmlsoap.org/soap/envelope xmlns=“http://www.smallco.org/order” xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance”> <SOAP:Header> <msg:MessageHeader xmlns:msg=“http://www.sterlingcommerce.com/message”> <msh:From>SterlingVommerce</msg:From> <msg:To>SmallCo</msg:To> <msg:Service>Purchase</msg:Service> <msg:Action>Order</msg:Action> <msg:MessageId>bbc006751</msg:MessageId> </msg:MessageHeader> </SOAP:Header> <SOAP:Body> <PurchaseOrder SOAP:encodingStyle=http://schemas.xmlsoap.org/soap/encoding/”> <PartnerID> <Name>Small Co Enterprise</Name> <ID type=“D-U-N-S+4”>123456789-0456</ID> </PartnerID> <Contact>John Adams</Contact> <Telephone>214-340-1234</Telephone> <Order> … </Order> <ShipInfo> … </ShipInfo> </PurchaseOrder> </SOAP:Body> </SOAP:Envelope> A SOAP Message EB & SWS

  8. Web Services EB & SWS

  9. Introduction to Semantic Web • Facilities to put machine-understandable data on the Web are becoming a high priority for many communities. • The Web can reach its full potential only if it becomes a place where data can be shared and processed by automated tools as well as by people. • For the Web to scale, tomorrow's programs must be able to share and process data even when these programs have been designed totally independently. EB & SWS

  10. Introduction to Semantic Web • The Semantic Web is a vision: 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 • See “W3C Semantic Web Activity,” by Marja-Riitta Koivunen, for more descriptions. EB & SWS

  11. The Semantic Web Layered Architecture Trust Proof Sig Tim Berners-Lee: “Axioms, Architecture and Aspirations” W3C all-working group plenary Meeting 28 February 2001 Logic Rules Ontology RDF Schema (http://www.w3.org/2001/Talks/0228-tbl/slide5-0.html) RDF M&S XML Schema XML Namespaces URI Unicode EB & SWS

  12. The Big Picture of SW EB & SWS

  13. Ontology Basics

  14. Why Develop an Ontology • Reasons why developing an ontology: • To share common understanding of the structure of information among people or software agents • To enable reuse of domain knowledge • To make domain assumptions explicit • To separate domain knowledge from the operational knowledge • To analyze domain knowledge EB & SWS

  15. Ontologies • One widely cited definition of an ontology is Gruber’s [Gruber 1993] “A specification of a conceptualization”. EB & SWS

  16. Ontologies • Ontologies can be used to provide a concrete specification of term names and term meanings. EB & SWS

  17. What Is in an Ontology? • For the purposes of this guide an ontology is a formal explicit description of • concepts in a domain of discourse (classes (sometimes called concepts)), • properties of each concept describing various features and attributes of the concept (slots (sometimes called roles or properties)), and • restrictions on slots (facets (sometimes called role restrictions)). • An ontology together with a set of individual instances of classes constitutes a knowledge base. EB & SWS

  18. A Simple Knowledge-Engineering Methodology • There is no one “correct” way or methodology for developing ontologies. • Here we discuss general issues to consider and offer one possible process for developing an ontology. EB & SWS

  19. A Simple Knowledge-Engineering Methodology Step 1:Determine the domain and scope of the ontology Step 2: Consider reusing existing ontologies Step 3:Enumerate important terms in the ontology Step 4: Define the classes and the class hierarchy Step 5: Define the properties of classes—slots Step 6:Define the facets of the slots Step 7: Create instances EB & SWS

  20. Uses Cases of Web Ontologies • Web portal • Multimedia collections • Corporate web site management • Design documentation • Agents and services • Ubiquitous computing EB & SWS

  21. XML-Based Ontology Languages

  22. 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) EB & SWS

  23. 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 EB & SWS

  24. Ora Lassila 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 s:Creator http://www.w3.org/Home/Lassila EB & SWS

  25. Another Example • To add properties to Creator, point through an intermediate Resource. http://www.w3.org/Home/Lassila s:Creator Person://fi/654645635 Name Email Ora Lassila lassila@w3.org EB & SWS

  26. /courses/6.001 Example: Bag • The students incourse 6.001 are Amy, Tim,John, Mary,and Sue Rdf:Bag rdf:type /Students/Amy students rdf:_1 rdf:_2 /Students/Tim bagid1 rdf:_3 /Students/John rdf:_4 /Students/Mary rdf:_5 /Students/Sue EB & SWS

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

  28. RDF Syntax I • Data model does not enforce particular syntax • Specification suggests many different syntaxes based on XML • General form: Subject (OID) Starts an RDF-Description <rdf:RDF> <rdf:Description about="http://www.w3.org/Home/Lassila"> <s:Creator>Ora Lassila</s:Creator> <s:createdWith rdf:resource=“http://www.w3c.org/amaya”/> </rdf:Description> </rdf:RDF> Literal Resource (possibly another RDF-description) Properties EB & SWS

  29. Resulting Graph http://www.w3.org/Home/Lassila s:createdWith s:Creator http://www.w3c.org/amaya Ora Lassila <rdf:RDF> <rdf:Description about="http://www.w3.org/Home/Lassila"> <s:Creator>Ora Lassila</s:Creator> <s:createdWith rdf:resource=“http://www.w3c.org/amaya”/> </rdf:Description> </rdf:RDF> EB & SWS

  30. RDF Syntax II: Syntactic Varieties Typing Information Subject (OID) In-Element Property <s:Homepage rdf:about="http://www.w3.org/Home/Lassila” s:Creator=“Ora Lassila”/> <s:createdWith> <s:HTMLEditor rdf:about=“http://www.w3c.org/amaya”/> </s:createdWith> </s:Homepage> rdf:type s:Homepage http://www.w3.org/Home/Lassila Property s:createdWith s:Creator rdf:type HTMLEditor http://www.w3c.org/amaya Ora Lassila EB & SWS

  31. 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. EB & SWS

  32. 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) EB & SWS

  33. DAML+OIL: an Ontology Language • Extension of RDF Schema • Ontology Language DAML+OIL: Result of a Joint (European + US-American) Committee • Extension of RDF Schema • Class Expressions (Intersection, Union, Complement) • XML Schema Datatypes • Enumerations • Property Restrictions • Cardinality Constraints • Value Restrictions EB & SWS

  34. OWLW3C Web Ontology Language • OWL provides three increasingly expressive sublanguages: OWL Lite, OWL DL, and OWL Full. EB & SWS

  35. OWLW3C 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 EB & SWS

  36. DAML-S: An Ontology for Semantic web Service

  37. DAML-S • Users and software agents should be able to discover, invoke, compose, and monitor Web resources offering particular services and having particular properties. • As part of the DARPA Agent Markup Language program, we have begun to develop an ontology of services, called DAML-S. EB & SWS

  38. Top Level of the Service Ontology Resource provides ServiceProfile presents (what it does) Service (how it works) (how to access it) supports described by ServiceGrounding ServiceModel EB & SWS

  39. Process Modeling Ontology EB & SWS

  40. Semantic Web Portal

  41. Web Portals • A web portal is a web site that provides information content on a common topic. • General portals, e.g., Yahoo, Excite, Netscape, Lycos, CNET, MSN, and AOL.com • Specialized portal e.g., gardeners.com, semanticweb.org • Making valuable information to be found • directory service, • search facility • news, e-mail, • community forum EB & SWS

  42. KA2 An Ontology-Based Community Web Portal

  43. Ontology-Based Web Portals • Ontology represents • common knowledge and interests sharing within their community • Tasks that ontology can be used to support a portal • Accessing a portal • Conceptual search and navigation • Inference capabilities • Providing information • Methods and tools accounting for the diversity of information sources EB & SWS

  44. 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. EB & SWS

  45. The KA2 Ontology Person-ontology Publication-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 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, … EB & SWS

  46. Accessing the Community Web Portal • Query capability • In F-Logic mechanism • Navigating capability • As the easy-to-use front-end of the query mechanism EB & SWS

  47. Development of Web Portals EB & SWS

  48. The System Architecture EB & SWS

  49. 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) EB & SWS

  50. Sesame’s Architecture EB & SWS

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