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Semantic Web Portal

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. Outline. A brief description to the Semantic Web Portal Architectural basis of the Semantic Web

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Semantic Web Portal

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  1. 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. Outline • A brief description to the Semantic Web Portal • Architectural basis of the Semantic Web • KA2: an ontology-based web portal • An architecture of RDF triple data store • Conclusions Semantic Web Portal

  3. 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. Semantic Web Portal

  4. 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. Semantic Web Portal

  5. 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 Semantic Web Portal

  6. Increasing demand for formalized knowledge on the Web: AI’s chance! XML- & RDF-based markup languages provide a 'universal' storage/interchange format for such Web-distributed knowledge representation. AI’s Chance Namespaces CSS DTDs XSLT DAML Stylesheets Agents Transformations Ontobroker XQL XML HornML Rules Queries XQuery RuleML XML-QL SHOE RDF[S] Frames Acquisition TopicMaps Protégé Semantic Web Portal

  7. The Big Picture of SW

  8. 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 Semantic Web Portal

  9. What is a portal? • In it's simplest form a portal is a filter for web content - a place from which users can locate all the Web resources that they commonly need. • Good portals are very successful at building online communities by bringing like-minded people together in one place. • As these communities are created, portal owners strive to offer a broader range of additional services in an attempt to hold on to their audiences for as long as possible. Semantic Web Portal

  10. What is a Subject Portal? • A Subject Portal could also be described as a 'vertical portal'. • Rather than a gateway to all Web content, a subject portal presents a tailored view of the Web within a common subject area. • From an academic perspective, the desire for detail and depth is far too great and the desired information far too hidden, for conventional portal services to satisfy these communities. Semantic Web Portal

  11. 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 Semantic Web Portal

  12. Trust Proof Sig Logic Rules Ontology RDF Schema RDF M&S XML Schema XML Namespaces URI Unicode Introduction to XML-Based Ontology Semantic Web Portal

  13. 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 Semantic Web Portal

  14. Namespace Bindings • Prefixes are bound to namespace URIs by attaching an xmlns:prefix attribute to the prefixed element or one of its ancestors, prefix:name1 ,...,prefix:namen • The value of the xmlns:prefix attribute is a URI, which may or (unlike for DTDs!) may not point to a description of the namespace’s syntax • An element can use bindings for multiple name-spaces via attributes xmlns:prefix1 ,...,xmlns:prefixm Semantic Web Portal

  15. XML Document Instance and DTD <mail:address xmlns:mail="http://www.deutschepost.de/" xmlns:tele="http://www.telekom.de/"> <mail:name>Xaver M. Linde</mail:name> <mail:street>Wikingerufer 7</mail:street> <mail:town>10555 Berlin</mail:town> <mail:bill>12.50</mail:bill> <tele:phone>030/1234567</tele:phone> <tele:phone>030/1234568</tele:phone> <tele:fax>030/1234569</tele:fax> <tele:bill>76.20</tele:bill> </ mail:address> <!ELEMENT address (name, street, town, bill, phone+, fax+, bill)> <!ELEMENT name (#PCDATA)> <!ELEMENT street (#PCDATA)> <!ELEMENT town (#PCDATA)> <!ELEMENT bill (#PCDATA)> <!ELEMENT phone (#PCDATA)> <!ELEMENT fax (#PCDATA)> <!ELEMENT ARTIST (#PCDATA)> Semantic Web Portal

  16. XML Schema • An XML syntax that's an alternative and/or supplement to DTDs • Data typing of element and attribute content Semantic Web Portal

  17. 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)

  18. 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 Semantic Web Portal

  19. 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 Semantic Web Portal

  20. 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 Semantic Web Portal

  21. /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 Semantic Web Portal

  22. 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 Semantic Web Portal

  23. 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 Semantic Web Portal

  24. 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> Semantic Web Portal

  25. 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

  26. 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. Semantic Web Portal

  27. 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) Semantic Web Portal

  28. 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 Semantic Web Portal

  29. Example: Intersection & Synonyms <daml:Class rdf:ID="TallMan"> <daml:intersectionOf rdf:parseType="daml:collection"> <daml:Class rdf:about="#TallThing"/> <daml:Class rdf:about="#Man"/> </daml:intersectionOf> </daml:Class> <daml:Class rdf:ID="HumanBeing"> <daml:sameClassAs rdf:resource="#Person"/> </daml:Class> Semantic Web Portal

  30. Example: Disjoint & Complement <daml:Disjoint rdf:parseType="daml:collection"> <daml:Class rdf:about="#Car"/> <daml:Class rdf:about="#Person"/> <daml:Class rdf:about="#Plant"/> </daml:Disjoint> Disjoint not strictly necessary, since expressible via pairwise subClassOf of complementOf, as for Car and Person: <daml:Class rdf:ID="Car"> <rdfs:comment>no car is a person</rdfs:comment> <rdfs:subClassOf> <daml:Class> <daml:complementOf rdf:resource="#Person"/> </daml:Class> </rdfs:subClassOf> </daml:Class> Semantic Web Portal

  31. Example: Properties (Transitive, Inverse, subProperty, UniqueProperty, range, Datatypes) <daml:TransitiveProperty rdf:ID="hasAncestor"/> <daml:ObjectProperty rdf:ID="hasChild"> <daml:inverseOf rdf:resource="#hasParent"/> </daml:ObjectProperty> <daml:UniqueProperty rdf:ID="hasMother"> <rdfs:subPropertyOf rdf:resource="#hasParent"/> <rdfs:range rdf:resource="#Female"/> </daml:UniqueProperty> <daml:DatatypeProperty rdf:ID="age"> <rdf:type rdf:resource="http://www.daml.org/2001/03/daml+oil#UniqueProperty"/> <rdfs:range rdf:resource="http://www.w3.org/.../XMLSchema#nonNegativeInteger"/> </daml:DatatypeProperty> Semantic Web Portal

  32. Using User-defined Datatypes(based on XML Schema) <xsd:simpleType name="over17"> <!--over17 is an XMLS datatype based on decimal--> <!--with the added restriction that values must be >=18--> <xsd:restriction base="xsd:decimal"> <xsd:minInclusive value="18"/> </xsd:restriction> </xsd:simpleType> <daml:Class rdf:ID="Adult"> <daml:intersectionOf rdf:parseType="daml:collection"> <daml:Class rdf:about="#Person"/> <daml:Restriction> <daml:onProperty rdf:resource="#age"/> <daml:hasClass rdf:resource="somefile#over17"/> </daml:Restriction> </daml:intersectionOf> </daml:Class> Semantic Web Portal

  33. Instances (Individuals) <daml:Class rdf:ID="Person"> . . . </daml:Class> <Person rdf:ID="Adam"> <rdfs:label>Adam</rdfs:label> <rdfs:comment>Adam is a person.</rdfs:comment> <age><xsd:integer rdf:value="13"/></age> <shoesize> <xsd:decimal rdf:value="9.5"/> </shoesize> </Person> Semantic Web Portal

  34. Web Services Semantic Web Portal

  35. 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. Semantic Web Portal

  36. 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 Semantic Web Portal

  37. Process Modeling Ontology Semantic Web Portal

  38. Concept of ebXML Business Process Specification Schema Semantic Web Portal

  39. Business Process Specification in XML Semantic Web Portal

  40. KA2 An Ontology-Based Community Web Portal

  41. 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. Semantic Web Portal

  42. 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, …

  43. Accessing the Community Web Portal • Query capability • In F-Logic mechanism • Navigating capability • As the easy-to-use front-end of the query mechanism Semantic Web Portal

  44. Query Capabilities FORALL Pub <- EXISTS ResID ResID:Researcher[NAME->> Steffen "Staab"; PUBLICATION ->> Pub]. For all publications of the researcher “Steffen Staab”. Two researchers cooperate, if a Researcher X works at a Project Proj and if a Researcher Y works at the same Project Proj and X is another person than Y FORALL X; Y; Proj X:Researcher[COOPERATESWITH ->> Y:Researcher] <- X:Researcher[WORKSATPROJECT->>Proj:Project] AND Y:Researcher[WORKSATPROJECT->>Proj:Project] AND NOT equal(X; Y ): Which researchers are cooperating with other r? FORALL ResID1, ResID2 <- ResID1:Researcher[COOPERATESWITH ->> ResID2]. Semantic Web Portal

  45. Navigating and Querying the Portal • Query the portal using F-Logic is too inconvenient. • Navigating and querying the web • A hypertext link may contain a query dynamically evaluated when clicking on the link (See P. 45) • Query generated by using the hyperbolic view interface (See P. 46) • Queries may be personalized and for the different users and available for the user in a selection list. • An expert mode: Querying the portal by typing an F-Logic statement Semantic Web Portal

  46. 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 Semantic Web Portal

  47. Metadata-based Information In RDF, XML Metadata Information source Annotation tool (OntoPad Annotea, …) Semantic Web Portal

  48. Wrapper-based Information • Annotating information sources by hand is time-consuming. Semi-structured Information sources (e.g., HTML) Wrapper program Metadata Structured Information sources (e.g., RDB) (Onto Wrapper) Semantic Web Portal

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