W3C Tracking – OWL

1. W3C Tracking – OWL David De Roure GGF Semantic Grid Research Group www.semanticgrid.org/GGF

2. XML+RDF Basics • URI - Uniform Resource Identifier • XML - eXtensible Markup Language • XML Namespaces • XML Schema • RDF - Resource Description Framework • RDF Schema GGF7 Tokyo March 2004

3. Resource Description Framework GGF7 Tokyo March 2004

4. Not Rocket Science “Is this rocket science? Well, not really. The Semantic Web, like the World Wide Web, is just taking well established ideas, and making them work interoperability over the Internet. This is done with standards, which is what the World Wide Web Consortium is all about. We are not inventing relational models for data, or query systems or rule-based systems. We are just webizing them. We are just allowing them to work together in a decentralized system - without a human having to custom handcraft every connection.” -- Tim Berners-Lee, Business Case for the Semantic Web, http://www.w3.org/DesignIssues/Business GGF7 Tokyo March 2004

5. Jargon interop In science, models provide interoperability across jargons • Mathematical models: equations of a system • Physical models: “sticks and balls” of the atom • Virtual models: the visualization of a complex data set • INFORMATION MODELS: taxonomies and thesauri GGF7 Tokyo March 2004

6. Ontologies • Ontologies extend thesaurus information models to provide • Semantic restrictions on property relations • Must have vs. May have vs. Doesn’t have • Has some vs. has N vs. has 1 • Some vs. All property restrictions • Formal underpinnings • Note: rules, logics, proofs are parts of ontologies, but not yet at a “consensus” level for standardization GGF7 Tokyo March 2004

7. RDFS • The Resource Description Framework (RDF) was the first language specified by the W3C for representing semantic information about arbitrary resources. • RDF Schema (RDFS) is a W3C candidate recommendation for an extension to RDF to describe RDF vocabularies. • RDFS can be used to create ontologies, but it is purposefully lightweight, with less expressive power than OWL. GGF7 Tokyo March 2004

8. Other ontology efforts • DAML - DARPA Agent Markup Language • DAML-ONT • MCF - Meta Content Framework. • Ontobroker • On-To-Knowledge • OIL - Ontology Inference Layer • SHOE - Simple HTML Ontology Extensions • XOL GGF7 Tokyo March 2004

9. DAML+OIL • Researchers, including many of the main participants in both the OIL and DAML-ONT efforts, got together in the Joint US/EU ad hoc Agent Markup Language Committee to create a new web ontology language • This language DAML+OIL built on both OIL and DAML-ONT, was submitted to the W3C as a proposed basis for OWL, and was subsequently selected as the starting point for OWL GGF7 Tokyo March 2004

10. DAML+OIL uptake DAML+OIL is already the most used ontology language in history • Sept 30, 02: Crawler finds 5M+ DAML statements on 20,000+ web pages • Doesn’t include many instance KBs tied to ontologies • Doesn’t include many very large RDFS-based KBs that include some OWL • OWL is being supported by large corporation labs • Web tool developers: IBM, HP, Sun, Intel, Fujitsu • Content providers: Daimler-Chrysler, Nokia, Motorola, EDS, Agfa • OWL is starting to be used by thesaurus distributors • C.f. National Cancer Institute metathesaurus to be released in OWL GGF7 Tokyo March 2004

11. OWL OWL Web Ontology Language GGF7 Tokyo March 2004

12. OWL Extends RDF • RDF-schema • Class, subclass • Property, subproperty + Restrictions • Range, domain • Local, global • Existential • Cardinality + Combinators Union, Intersection Complement Symmetric, transitive + Mapping Equivalence Inverse GGF7 Tokyo March 2004

13. OWL is not • OWL is not a “knowledge representation language” per se • Definitely not “The standard: for KR” • OWL is not a “Description Logic” per se • It does support DL “idioms” • E.g. “Lymphoma” is restricted to be a subClassOf those things whose “disease” property is “Cancer” • It includes a “subset” which is complete, and decidable • But, it will allow uses that DLs do not GGF7 Tokyo March 2004

14. OWL Documents • Web Ontology Language (OWL) Guide Version 1.0, W3C Working Draft, 26 February 2003 • Requirements for a Web Ontology Language. W3C Working Draft, 08 July 2002. • Feature Synopsis for OWL Lite and OWL. Deborah L. McGuinness and Frank van Harmelen. W3C Working Draft, 29 Jul 2002. • OWL Web Ontology Language 1.0 Reference. Mike Dean and Guus Schreiber. W3C Working Draft, 3 February 2003. • OWL Web Ontology Language 1.0 Abstract Syntax. Peter F. Patel-Schneider, Ian Horrocks, and Frank van Harmelen. W3C Working Draft 29 July 2002. • Model-Theoretic Semantics for OWL, Peter F. Patel-Schneider, Partick Hayes, and Ian Horrocks. 3 February 2003 GGF7 Tokyo March 2004

15. OWL Guide This document demonstrates the use of the OWL language to • formalize a domain by defining classes and properties of those classes, • define individuals and assert properties about them, and • reason about these classes and individuals to the degree permitted by the formal semantics of the OWL language. GGF7 Tokyo March 2004

16. The Species of OWL • OWL Lite supports those users primarily needing a classification hierarchy and simple constraint features. It should be simpler to provide tool support for OWL Lite than its more expressive relatives, and provides a quick migration path for thesauri and other taxonomies. GGF7 Tokyo March 2004

17. The Species of OWL • OWL DL supports those users who want the maximum expressiveness without losing computational completeness and decidability of reasoning systems. OWL DL was designed to support the existing Description Logic business segment. GGF7 Tokyo March 2004

18. The Species of OWL • OWL Full is meant for users who want maximum expressiveness and the syntactic freedom of RDF with no computational guarantees. It allows an ontology to augment the meaning of the pre-defined (RDF or OWL) vocabulary. GGF7 Tokyo March 2004

19. Expressiveness • OWL Lite supports cardinality constraints, but it only permits cardinality values of 0 or 1. • In OWL DL, a class cannot also be an individual or property, a property can not also be an individual or class. • In OWL Full a class can be treated simultaneously as a collection of individuals and as an individual in its own right. GGF7 Tokyo March 2004

20. See some OWL! • Fragments from the Wine Ontology example in the OWL Guide… GGF7 Tokyo March 2004

21. Namespaces <rdf:RDF xmlns =http://www.example.org/wine# xmlns:vin =http://www.example.org/wine# xmlns:food=http://www.example.org/food# xmlns:owl ="http://www.w3.org/2002/07/owl#" xmlns:rdf =http://www.w3.org/1999/02/22-rdf-syntax-ns# xmlns:rdfs=http://www.w3.org/2000/01/rdf-schema# xmlns:xsd ="http://www.w3.org/2000/10/XMLSchema#"> GGF7 Tokyo March 2004

22. Ontology header <owl:Ontology rdf:about="http://www.example.org/wine"> <rdfs:comment>An example OWL ontology</rdfs:comment> <owl:priorVersion rdf:resource="http://www.example.org/wine-2102.owl"/> <owl:imports rdf:resource="http://www.example.org/food.owl"/> <rdfs:label>Wine Ontology</rdfs:label> ... </owl:Ontology> GGF7 Tokyo March 2004

23. Simple classes <owl:Class rdf:ID="Winery"/> <owl:Class rdf:ID="Region"/> <owl:Class rdf:ID="ConsumableThing"/> <owl:Class rdf:ID="Wine"> <rdfs:subClassOf rdf:resource="&food;PotableLiquid"/> <rdfs:label xml:lang="en">wine</rdfs:label> <rdfs:label xml:lang="fr">vin</rdfs:label> ... </owl:Class> GGF7 Tokyo March 2004

24. Tools • Being able to express ontologies is not enough…we need tools! • Existing tools, especially DAML+OIL, are adapting to OWL • Available for use in the lifetime of this group GGF7 Tokyo March 2004

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26. Conclusions • OWL is more expressive than RDF(S) • OWL evolved from DAML+OIL • There are three species of OWL • OWL nearing completion and documents are available • See OWL Guide for examples • Tools are increasingly available GGF7 Tokyo March 2004

27. Acknowledgements These slides are primarily based on the OWL Guide and on a presentation by Jim Hender GGF7 Tokyo March 2004