W3C Tracking OWL

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W3C Tracking OWL

• David De Roure
• GGF Semantic Grid Research Group
• www.semanticgrid.org/GGF

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XMLRDF Basics

• URI - Uniform Resource Identifier
• XML - eXtensible Markup Language
• XML Namespaces
• XML Schema
• RDF - Resource Description Framework
• RDF Schema

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Resource Description Framework
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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
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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

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Ontologies

• Ontologies extend thesaurus information models to
  provide
• Semantic restrictions on property relations
• Must have vs. May have vs. Doesnt 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

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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.

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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

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DAMLOIL

• 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 DAMLOIL 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

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DAMLOIL uptake

• DAMLOIL is already the most used ontology
  language in history
• Sept 30, 02 Crawler finds 5M DAML statements on
  20,000 web pages
• Doesnt include many instance KBs tied to
  ontologies
• Doesnt 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

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OWL Web Ontology Language
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OWL Extends RDF

• RDF-schema
• Class, subclass
• Property, subproperty
• Restrictions
• Range, domain
• Local, global
• Existential
• Cardinality

Combinators Union, Intersection Complement Symme
tric, transitive Mapping Equivalence Inverse
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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

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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

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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.

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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.

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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.

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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.

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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.

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See some OWL!

• Fragments from the Wine Ontology example in the
  OWL Guide

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Namespaces

• ltrdfRDF xmlns http//www.example.org/wine
• xmlnsvin http//www.example.org/wine
• xmlnsfoodhttp//www.example.org/food
• xmlnsowl "http//www.w3.org/2002/07/owl"
• xmlnsrdf http//www.w3.org/1999/02/22-rdf-synta
  x-ns
• xmlnsrdfshttp//www.w3.org/2000/01/rdf-schema
• xmlnsxsd "http//www.w3.org/2000/10/XMLSchema"
  gt

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Ontology header

• ltowlOntology rdfabout"http//www.example.org/wi
  ne"gt
• ltrdfscommentgtAn example OWL ontologylt/rdfscomm
  entgt
• ltowlpriorVersion rdfresource"http//www.exampl
  e.org/wine-2102.owl"/gt
• ltowlimports rdfresource"http//www.example.org
  /food.owl"/gt
• ltrdfslabelgtWine Ontologylt/rdfslabelgt
• ...
• lt/owlOntologygt

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Simple classes

• ltowlClass rdfID"Winery"/gt
• ltowlClass rdfID"Region"/gt
• ltowlClass rdfID"ConsumableThing"/gt
• ltowlClass rdfID"Wine"gt
• ltrdfssubClassOf rdfresource"foodPotableLiqui
  d"/gt
• ltrdfslabel xmllang"en"gtwinelt/rdfslabelgt
• ltrdfslabel xmllang"fr"gtvinlt/rdfslabelgt
• ...
• lt/owlClassgt

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Tools

• Being able to express ontologies is not enoughwe
  need tools!
• Existing tools, especially DAMLOIL, are adapting
  to OWL
• Available for use in the lifetime of this group

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Conclusions

• OWL is more expressive than RDF(S)
• OWL evolved from DAMLOIL
• There are three species of OWL
• OWL nearing completion and documents are
  available
• See OWL Guide for examples
• Tools are increasingly available

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Acknowledgements

• These slides are primarily based on the OWL Guide
  and on a presentation by Jim Hender