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From SHIQ and RDF to OWL: The Making of a Web Ontology Language

From SHIQ and RDF to OWL: The Making of a Web Ontology Language. Ian Horrocks Peter F. Patel-Schneider and Frank van Harmelen Presented by Zonghui Lian. Ontology Languages. So far, how many ontology languages we can know XOL (XML-based Ontology Exchange Language)

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From SHIQ and RDF to OWL: The Making of a Web Ontology Language

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  1. From SHIQ and RDF to OWL:The Making of a Web Ontology Language Ian Horrocks Peter F. Patel-Schneider and Frank van Harmelen Presented by Zonghui Lian

  2. Ontology Languages • So far, how many ontology languages we can know • XOL (XML-based Ontology Exchange Language) • SHOE (Simple HTML Ontology Extension) • OML (Ontology Markup Language) • RDF(S) (Resource Description Framework (Schema)) • OIL (Ontology Interchange Language) • DAML+OIL (DARPA Agent Markup Language + OIL) • OWL (Ontology Web Language)

  3. XML – XML Schema • XML provides a standardized syntactical way to expose structural information • XML schema allows to define a schema for XML documents and may already provide machine-understandable semantics of data • Do not attach meaning to structural information

  4. RDF Schema • RDFS is too weak to describe resources in sufficient detail • No localised range and domain constraints • For example, can’t express such a subclass of person: the person who has children. • No existence/cardinality constraints • Can’t say that all instances of person have a mother that is also a person, or that persons have exactly 2 parents • No transitive, inverse or symmetrical properties • Can’t say that isPartOf is a transitive property, that hasPart is the inverse of isPartOf or that touches is symmetrical • Difficult to provide reasoning support

  5. Requirements Desirable features identified for a Web Ontology Language : • Compatiblewith existing Web standards (XML, RDF, RDFS) • Easy to understandand use • Formally specified • Has “adequate” expressive power • Tools for reasoning support

  6. Attribution Explanation We are here! Rules & Inference Ontologies Metadata Standard Syntax Identity Layers of Languages

  7. OWL (Ontology Web Language) • OWL is now a W3C Recommendation • The purpose of OWL is identical to RDFS i.e. to provide an XML vocabulary to define classes, properties and their relationships. • RDFS enables us to express basic relationships and has limited inferencing capability. • OWL enables us to express much richer relationships, thus yielding a much enhanced inferencing capability. • The benefit of OWL is that it facilitates a much greater degree of inferencing than you get with RDF Schema.

  8. Comparison RDF and OWL

  9. Introduction of OWL (Ontology Web Language) • Description logic and frames • Many characteristics of RDF

  10. D.L’s Influence on OWL • Semantics are well defined. • OWL uses D.L model theory to formalise the meaning of the language. • Advantages

  11. D.L’s Influence on OWL • Language constructors • Expressive power • Class (property) constructors • Axioms • Conflict with the computational complexity • OWL entailment • Blance

  12. D.L’s Influence on OWL • Datatypes • Difference with • Advantage • Decrease the complexity & easy to answer question “-5 nonNegative ?”

  13. Origins of OWL DARPA Agent Markup Language Ontology Inference Layer DAML OIL RDF EU/NSF Joint Ad hoc Committee DAML+OIL All influenced by RDF OWL Lite OWL DL OWL Full A W3C Recommendation OWL

  14. Versions of OWL Full: Consider the compatibility with RDF and RDFS as the primary importance. no computation guarantees DL (Description Logic): Friendly syntax, decidable inference. computationally complete Lite: Simpler syntax and more tractable inference. • Depending on the intended usage, OWL provides three increasingly expressive sublanguages OWL Full OWL DL OWL Lite

  15. Advantages/Disadvantages of versions • Full: • The advantage of the Full version of OWL is that we get the full power of the OWL language. • The disadvantage is that it is very difficult to build a computational tool for this version and may not get a quick and complete answer. • DL/Lite: • The advantage of the DL or Lite version of OWL is that tools can be built more quickly and easily, and users can expect responses from such tools to come quicker and be more complete. • The disadvantage is that we don't have access to the full power of the language.

  16. OWL as D.L

  17. OWL as D.L

  18. Conclusion • Difference b/w OWL DL & D.L: • Datatyping mechanisms (XML schema datatypes) • RDF URI reference as name • Entailments OWL DL is compatible with that of RDF and RDFS

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