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1336 lines
60 KiB
1336 lines
60 KiB
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>OWL Web Ontology Language Overview</title>
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<link
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href="http://www.w3.org/StyleSheets/TR/W3C-WD"
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type="text/css" rel="stylesheet" />
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<meta name="RCSId" content="$Id: Overview.html,v 1.7 2003/03/31 23:08:07 connolly Exp $"/>
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</head>
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<body lang="EN">
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<div class="head">
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<a href="http://www.w3.org/"><img height="48" alt="W3C"
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src="http://www.w3.org/Icons/w3c_home" width="72" /></a>
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<h1>OWL Web Ontology Language <br />Overview
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</h1>
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<h2><a id="w3c-doctype" name="w3c-doctype"></a>W3C Working
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Draft 31 March 2003</h2>
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<dl>
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<dt>This version:</dt>
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<dd><a
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href="http://www.w3.org/TR/2003/WD-owl-features-20030331/">http://www.w3.org/TR/2003/WD-owl-features-20030331/</a></dd>
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<dt>Latest version:</dt>
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<dd><a
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href="http://www.w3.org/TR/owl-features/">http://www.w3.org/TR/owl-features/</a></dd>
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<dt>Previous version:</dt>
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<dd><a
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href="http://www.w3.org/TR/2003/WD-owl-features-20030210/">http://www.w3.org/TR/2003/WD-owl-features-20030210/</a></dd>
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<dt>Editors:</dt>
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<dd>Deborah L. McGuinness (Knowledge Systems Laboratory,
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Stanford University) <a
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href="mailto:dlm@ksl.stanford.edu">dlm@ksl.stanford.edu</a></dd>
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<dd>Frank van Harmelen (Vrije Universiteit, Amsterdam) <a
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href="mailto:Frank.van.Harmelen@cs.vu.nl">Frank.van.Harmelen@cs.vu.nl</a></dd>
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</dl>
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<p class="copyright"><a
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href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">
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Copyright</a> ©2003 <a
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href="http://www.w3.org/"><acronym
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title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup>
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(<a href="http://www.lcs.mit.edu/"><acronym
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title="Massachusetts Institute of Technology">MIT</acronym></a>,
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<a href="http://www.ercim.org/"><acronym
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title="European Research Consortium for Informatics and Mathematics">
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ERCIM</acronym></a> , <a
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href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved.
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W3C <a
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href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">
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liability</a>, <a
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href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">
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trademark</a>, <a
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href="http://www.w3.org/Consortium/Legal/copyright-documents">
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document use</a> and <a
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href="http://www.w3.org/Consortium/Legal/copyright-software">software
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licensing</a> rules apply.</p>
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<hr title="Separator for header" />
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</div>
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<h2><a id="abstract" name="abstract">Abstract</a></h2>
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<p>The OWL Web Ontology Language is designed for use by
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applications that need to process the content of information
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instead of just presenting information to humans. OWL
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facilitates greater machine readability of Web content than
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that supported by XML, RDF, and RDF Schema by providing
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additional vocabulary along with a formal semantics. OWL has
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three increasingly-expressive sublanguages: OWL Lite, OWL DL,
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and OWL Full.</p>
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<p>This document is written for readers who want a first
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impression of the capabilities of OWL. It provides an
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introduction to OWL by informally describing the features of
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each of the sublanguages of OWL. Some knowledge of <a
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href="http://www.w3.org/TR/rdf-schema/">RDF Schema</a> is
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useful for understanding this document, but not essential.
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After this document, interested readers may turn to the <a
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href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/">OWL
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Guide</a> for a more detailed descriptions and extensive
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examples on the features of OWL. The normative formal
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definition of OWL can be found in the <a
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href="http://www.w3.org/TR/2002/WD-owl-semantics-20021108/">OWL
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Semantics and Abstract Syntax</a>.</p>
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<h2><a id="status" name="status"></a>Status of this
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document</h2>
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<div class="status">
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<p>This is a <a
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href="http://www.w3.org/Consortium/Process-20010719/tr.html#last-call">Last
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Call Working Draft</a>. The <a
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href="http://www.w3.org/TR/2002/WD-owl-features-20020729/">first release
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of this document</a> was 29 July 2002 and the <a
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href="http://www.w3.org/2001/sw/WebOnt">Web Ontology Working Group</a>
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has made its best effort to address <a
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href="http://lists.w3.org/Archives/Public/public-webont-comments/">comments
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recieved</a> since then, releasing several drafts and resolving a <a
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href="http://www.w3.org/2001/sw/WebOnt/webont-issues.html">list of
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issues</a> meanwhile. The working group seeks confirmation that
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comments have been addressed to the satisfaction of the community.</p>
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<p>This is a <b>non-normative</b> overview of OWL; it does not provide
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a definitive specification of OWL. The examples and other
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explanatory material herein are provided to help understand OWL,
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but may not always provide definitive or complete answers. The
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normative formal definition of OWL can be found in the <a
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href="http://www.w3.org/TR/owl-semantics/">OWL
|
|
Semantics and Abstract Syntax</a>.</p>
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<p>Comments on this document are due <span class="commentsDue
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date">9 May 2003</span>. They should be sent to the W3C mailing
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list <a
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href="mailto:public-webont-comments@w3.org">public-webont-comments@w3.org</a>
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(with <a
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href="http://lists.w3.org/Archives/Public/public-webont-comments/">
|
|
public archive</a>).</p>
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<p>
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This document has been produced as part of the <a
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href="http://www.w3.org/2001/sw/">W3C Semantic Web Activity</a> (<a
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href="http://www.w3.org/2001/sw/Activity">Activity Statement</a>).
|
|
A list of <a rel="disclosure"
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href="http://www.w3.org/2001/sw/WebOnt/discl">patent disclosures
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|
related to this work</a> is maintained by W3C, regardless of whether
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any such disclosures have been made or not.</p>
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<p><em>This section describes the status of this document at
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the time of its publication. Other documents may supersede
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this document. A list of current W3C Recommendations and
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other technical reports is available at <a
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href="http://www.w3.org/TR/">http://www.w3.org/TR/</a>.</em></p>
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</div>
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<h2><a id="contents" name="contents">Table of contents</a></h2>
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<ol>
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<li>
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<a
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href="http://www.w3.org/TR/owl-features/#s1">Introduction</a>
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<ol>
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<li><a
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href="http://www.w3.org/TR/owl-features/#s1.1">Document
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Roadmap</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s1.2">Why
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OWL?</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s1.3">The
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three sublanguages of OWL</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s1.4">The
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structure of this document</a></li>
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</ol>
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</li>
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<li>
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<a href="http://www.w3.org/TR/owl-features/#s2">Language
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Synopsis</a>
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<ol>
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<li><a href="http://www.w3.org/TR/owl-features/#s2.1">OWL
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Lite Synopsis</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s2.2">OWL
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DL and OWL Full Synopsis</a></li>
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</ol>
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</li>
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<li>
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<a href="http://www.w3.org/TR/owl-features/#s3">Language
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Description of OWL Lite</a>
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<ol>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.1">OWL
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Lite RDF Schema Features</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.2">OWL
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Lite Equality and Inequality</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.3">OWL
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Lite Property Characteristics</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.4">OWL
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Lite Property Type Restrictions</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.5">OWL
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Lite Restricted Cardinality</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.6">OWL
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Lite Class Intersection</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.7">OWL
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Datatypes</a></li>
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<li><a href="http://www.w3.org/TR/owl-features/#s3.8">OWL
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Lite Header Information</a></li>
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</ol>
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</li>
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<li><a
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href="http://www.w3.org/TR/owl-features/#s4">Incremental
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Language Description of OWL DL and OWL Full</a></li>
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<li><a
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href="http://www.w3.org/TR/owl-features/#s5">Summary</a></li>
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<li style="list-style: none"><br />
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<a
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href="http://www.w3.org/TR/owl-features/#s6">Acknowledgements</a></li>
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</ol>
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<hr />
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<h2><a id="s1" name="s1"></a>1. Introduction</h2>
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<p>This document describes the OWL Web Ontology Language. OWL
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is intended to be used when the information contained in
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documents needs to be processed by applications, as opposed to
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situations where the content only needs to be presented to
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humans. OWL can be used to explicitly represent the meaning of
|
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terms in vocabularies and the relationships between those
|
|
terms. This representation of terms and their
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|
interrelationships is called an ontology. OWL has more
|
|
facilities for expressing meaning and semantics than XML, RDF,
|
|
and RDF-S, and thus OWL goes beyond these languages in its
|
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ability to represent machine readable content on the Web. OWL
|
|
is a revision of the <a
|
|
href="http://www.w3.org/TR/daml+oil-reference">DAML+OIL web
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|
ontology language</a> incorporating lessons learned from the
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design and application of DAML+OIL.</p>
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<h3><a id="s1.1" name="s1.1"></a>1.1 Document Roadmap</h3>
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<p>The OWL Language is described by a set of documents, each
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fulfilling a different purpose, and catering for a different
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audience. The following provides a brief roadmap for navigating
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|
through this set of documents:</p>
|
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|
<ul>
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|
<li>This <a href="http://www.w3.org/TR/owl-features/">Owl
|
|
Overview</a> gives a simple introduction to OWL by providing
|
|
a language feature listing with very brief feature
|
|
descriptions;</li>
|
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|
<li>The <a href="http://www.w3.org/TR/owl-guide/">OWL
|
|
Guide</a> demonstrates the use of the OWL language by
|
|
providing an extended example. It also provides <a
|
|
href="http://www.w3.org/TR/owl-guide/#OWLGlossary">glossary</a>
|
|
of the terminology used in these documents;</li>
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|
|
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<li>The <a href="http://www.w3.org/TR/owl-ref/">OWL
|
|
Reference</a> gives a systematic and compact (but still
|
|
informally stated) description of all the modelling
|
|
primitives of OWL;</li>
|
|
|
|
<li>The <a href="http://www.w3.org/TR/owl-absyn/">OWL
|
|
Semantics and Abstract Syntax</a> document is the final and
|
|
formally stated normative definition of the language.</li>
|
|
</ul>
|
|
The suggested reading order of these documents is as given,
|
|
since they have been listed in increasing degree of technical
|
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content.
|
|
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|
<h3><a id="s1.2" name="s1.2"></a>1.2 Why OWL?</h3>
|
|
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|
<p>The Semantic Web is a vision for the future of the Web in
|
|
which information is given explicit meaning, making it easier
|
|
for machines to automatically process and integrate information
|
|
available on the Web. The Semantic Web will build on XML's
|
|
ability to define customized tagging schemes and RDF's flexible
|
|
approach to representing data. The first level above RDF
|
|
required for the Semantic Web is an ontology language what can
|
|
formally describe the meaning of terminology used in Web
|
|
documents. If machines are expected to perform useful reasoning
|
|
tasks on these documents, the language must go beyond the basic
|
|
semantics of RDF Schema. The <a
|
|
href="http://www.w3.org/TR/webont-req/">OWL Use Cases and
|
|
Requirements Document</a> provides more <a
|
|
href="http://www.w3.org/TR/webont-req/#onto-def">details on
|
|
ontologies</a>, motivates the need for a Web Ontology Language
|
|
in terms of <a
|
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href="http://www.w3.org/TR/webont-req/#section-use-cases">six
|
|
use cases</a>, and formulates <a
|
|
href="http://www.w3.org/TR/webont-req/#section-goals">design
|
|
goals</a>, <a
|
|
href="http://www.w3.org/TR/webont-req/#section-requirements">requirements</a>
|
|
and <a
|
|
href="http://www.w3.org/TR/webont-req/#section-objectives">objectives</a>
|
|
for OWL.</p>
|
|
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|
<p>OWL has been designed to meet this need for a Web Ontology
|
|
Language. OWL is part of the growing stack of W3C
|
|
recommendations related to the Semantic Web.</p>
|
|
|
|
<ul compact="compact">
|
|
<li>
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|
<p><a href="http://www.w3.org/XML/">XML</a> provides a
|
|
surface syntax for structured documents, but imposes no
|
|
semantic constraints on the meaning of these documents.</p>
|
|
</li>
|
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<li>
|
|
<p><a href="http://www.w3.org/XML/Schema">XML Schema</a> is
|
|
a language for restricting the structure of XML
|
|
documents.</p>
|
|
</li>
|
|
|
|
<li>
|
|
<p><a
|
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href="http://www.w3.org/TR/2002/WD-rdf-concepts-20021108/">RDF</a>
|
|
is a datamodel for objects ("resources") and relations
|
|
between them, provides a simple semantics for this
|
|
datamodel, and these datamodels can be represented in an
|
|
XML syntax.</p>
|
|
</li>
|
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|
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<li>
|
|
<p><a
|
|
href="http://www.w3.org/TR/2002/WD-rdf-schema-20021112/">RDF
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Schema</a> is a vocabulary for describing properties and
|
|
classes of RDF resources, with a semantics for
|
|
generalization-hierarchies of such properties and
|
|
classes.</p>
|
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</li>
|
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|
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<li>
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<p>OWL adds more vocabulary for describing properties and
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classes: among others, relations between classes (e.g.
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|
disjointness), cardinality (e.g. "exactly one"), equality,
|
|
richer typing of properties, characteristics of properties
|
|
(e.g. symmetry), and enumerated classes.</p>
|
|
</li>
|
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</ul>
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<br />
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<br />
|
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|
|
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<h3><a id="s1.3" name="s1.3"></a>1.3 The three sublanguages of
|
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OWL</h3>
|
|
|
|
<p>OWL provides three increasingly expressive sublanguages
|
|
designed for use by specific communities of implementers and
|
|
users.</p>
|
|
|
|
<ul>
|
|
<li>
|
|
<p><a id="term_OWLLite" name="term_OWLLite"></a><em>OWL
|
|
Lite</em> supports those users primarily needing a
|
|
classification hierarchy and simple constraints. For
|
|
example, while it supports cardinality constraints, it only
|
|
permits cardinality values of 0 or 1. It should be simpler
|
|
to provide tool support for OWL Lite than its more
|
|
expressive relatives, and OWL Lite provides a quick
|
|
migration path for thesauri and other taxonomies.</p>
|
|
</li>
|
|
|
|
<li>
|
|
<p><a id="term_OWLDL" name="term_OWLDL"></a><em>OWL DL</em>
|
|
supports those users who want the maximum expressiveness
|
|
while retaining computational completeness (all conclusions
|
|
are guaranteed to be computed) and decidability (all
|
|
computations will finish in finite time). OWL DL includes
|
|
all OWL language constructs, but they can be used only
|
|
under certain restrictions (for example, while a class may
|
|
be a subclass of many classes, a class cannot be an
|
|
instance of another class).
|
|
<!-- FvH: DELETED because too technical
|
|
with restrictions such as type separation (a class can not also be an individual or
|
|
property, a property can not also be an individual or class).
|
|
-->OWL DL is so named due to its correspondence with <a
|
|
href="http://dl.kr.org/"><em>description logics</em></a>, a
|
|
field of research that has studied the logics that form the
|
|
formal foundation of OWL.</p>
|
|
</li>
|
|
|
|
<li>
|
|
<p><a id="term_OWLFull" name="term_OWLFull"></a><em>OWL
|
|
Full</em> is meant for users who want maximum
|
|
expressiveness and the syntactic freedom of RDF with no
|
|
computational guarantees. For example, in OWL Full a class
|
|
can be treated simultaneously as a collection of
|
|
individuals and as an individual in its own right. OWL Full
|
|
allows an ontology to augment the meaning of the
|
|
pre-defined (RDF or OWL) vocabulary. It is unlikely that
|
|
any reasoning software will be able to support complete
|
|
reasoning for every feature of OWL Full.</p>
|
|
</li>
|
|
</ul>
|
|
|
|
<p>Each of these sublanguages is an extension of its simpler
|
|
predecessor, both in what can be legally expressed and in what
|
|
can be validly concluded. The following set of relations hold.
|
|
Their inverses do not.</p>
|
|
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|
<ul>
|
|
<li>Every legal OWL Lite ontology is a legal OWL DL
|
|
ontology.</li>
|
|
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|
<li>Every legal OWL DL ontology is a legal OWL Full
|
|
ontology.</li>
|
|
|
|
<li>Every valid OWL Lite conclusion is a valid OWL DL
|
|
conclusion.</li>
|
|
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|
<li>Every valid OWL DL conclusion is a valid OWL Full
|
|
conclusion.</li>
|
|
</ul>
|
|
|
|
<p>Ontology developers adopting OWL should consider which
|
|
sublanguage best suits their needs. The choice between OWL Lite
|
|
and OWL DL depends on the extent to which users require the
|
|
more-expressive constructs provided by OWL DL and OWL Full. The
|
|
choice between OWL DL and OWL Full mainly depends on the extent
|
|
to which users require the meta-modeling facilities of RDF
|
|
Schema (e.g. defining classes of classes, or attaching
|
|
properties to classes). When using OWL Full as compared to OWL
|
|
DL, reasoning support is less predictable since complete OWL
|
|
Full implementations do not currently exist.</p>
|
|
OWL Full can be viewed as an extension of RDF, while OWL Lite
|
|
and OWL DL can be viewed as extensions of a restricted view of
|
|
RDF. Every OWL (Lite, DL, Full) document is an RDF document,
|
|
and every RDF document is an OWL Full document, but only some
|
|
RDF documents wll be a legal OWL Lite or OWL DL document.
|
|
|
|
<h3><a id="s1.4" name="s1.4"></a>1.4 The structure of this
|
|
document</h3>
|
|
|
|
<p>This document first describes the features from OWL Lite,
|
|
followed by a description from the features that are added in
|
|
OWL DL and OWL Full (OWL DL and OWL Full contain the same
|
|
features, but OWL Full is more liberal about how these features
|
|
can be combined).</p>
|
|
|
|
<h2><a id="s2" name="s2"></a>2. Language Synopsis</h2>
|
|
This section provides a quick index to all the language
|
|
features for OWL Lite, OWL DL, and OWL Full.
|
|
|
|
<p>In this document, italicized terms are terms in OWL.
|
|
Prefixes of rdf: or rdfs: are used when terms are already
|
|
present in RDF or RDF Schema. Otherwise terms are introduced by
|
|
OWL. Thus, the term <i>rdfs:subPropertyOf</i> indicates that
|
|
subPropertyOf is already in the rdfs vocabulary (technically :
|
|
the rdfs namespace). Also, the term <i>Class</i> is more
|
|
precisely stated as <i>owl:Class</i> and is a term introduced
|
|
by OWL.</p>
|
|
|
|
<h3><a id="s2.1" name="s2.1"></a>2.1 OWL Lite Synopsis</h3>
|
|
|
|
<p>The list of OWL Lite language constructs is given below.</p>
|
|
|
|
<table cellspacing="30" width="100%">
|
|
<colgroup span="4" width="1">
|
|
</colgroup>
|
|
|
|
<tbody>
|
|
<tr>
|
|
<td class="index" valign="top">
|
|
<b>RDF Schema Features:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#Class">Class</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#property">rdf:Property</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#subClassOf">rdfs:subClassOf</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#subPropertyOf">
|
|
rdfs:subPropertyOf</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#domain">rdfs:domain</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#range">rdfs:range</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#Individual">Individual</a></i></li>
|
|
</ul>
|
|
</td>
|
|
|
|
<td class="index" valign="top">
|
|
<b>(In)Equality:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#equivalentClass">
|
|
equivalentClass</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#equivalentProperty">
|
|
equivalentProperty</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#sameIndividualAs">
|
|
sameIndividualAs</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#differentFrom">
|
|
differentFrom</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#allDifferent">
|
|
allDifferent</a></i></li>
|
|
</ul>
|
|
</td>
|
|
|
|
<td class="index" valign="top">
|
|
<b>Property Characteristics:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#inverseOf">inverseOf</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#TransitiveProperty">
|
|
TransitiveProperty</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#SymmetricProperty">
|
|
SymmetricProperty</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#FunctionalProperty">
|
|
FunctionalProperty</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#InverseFunctionalProperty">
|
|
InverseFunctionalProperty</a></i></li>
|
|
</ul>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
|
|
<tbody>
|
|
<tr>
|
|
<td class="index" valign="top">
|
|
<b>Property Type Restrictions:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#allValuesFrom">
|
|
allValuesFrom</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#someValuesFrom">
|
|
someValuesFrom</a></i></li>
|
|
</ul>
|
|
<br />
|
|
<br />
|
|
<b>Class Intersection:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#intersectionOf">
|
|
intersectionOf</a></i></li>
|
|
</ul>
|
|
</td>
|
|
|
|
<td class="index" valign="top">
|
|
<b>Restricted Cardinality:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#minCardinality">
|
|
minCardinality</a></i> (only 0 or 1)</li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#maxCardinality">
|
|
maxCardinality</a></i> (only 0 or 1)</li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#Cardinality">
|
|
cardinality</a></i> (only 0 or 1)</li>
|
|
</ul>
|
|
<br />
|
|
<b><a
|
|
href="http://www.w3.org/TR/owl-features/#s3.7">Datatypes</a></b>
|
|
</td>
|
|
|
|
<td class="index" valign="top">
|
|
<b>Header Information:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#s3.8">imports</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#s3.8">priorVersion</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#s3.8">backwardCompatibleWith</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#s3.8">incompatibleWith</a></i></li>
|
|
</ul>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<h3><a id="s2.2" name="s2.2"></a>2.2 OWL DL and Full
|
|
Synopsis</h3>
|
|
|
|
<p>The list of OWL DL and OWL Full language constructs that are
|
|
in addition to those of OWL Lite is given below.</p>
|
|
|
|
<table cellspacing="30" width="100%">
|
|
<colgroup span="4" width="1">
|
|
</colgroup>
|
|
|
|
<tbody>
|
|
<tr>
|
|
<td class="index" valign="top">
|
|
<b>Class Axioms:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#oneOf">oneOf</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#disjointWith">
|
|
disjointWith</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#complexClassFull">
|
|
equivalentClass</a></i><br />
|
|
(applied to class expressions)</li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#complexClassFull">
|
|
rdfs:subClassOf</a></i><br />
|
|
(applied to class expressions)</li>
|
|
</ul>
|
|
</td>
|
|
|
|
<td class="index" valign="top">
|
|
<b>Boolean Combinations of Class Expressions:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#booleanFull">
|
|
unionOf</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#booleanFull">
|
|
intersectionOf</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#booleanFull">
|
|
complementOf</a></i></li>
|
|
</ul>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
|
|
<tbody>
|
|
<tr>
|
|
<td class="index" valign="top">
|
|
<b>Arbitrary Cardinality:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#cardinalityFull">
|
|
minCardinality</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#cardinalityFull">
|
|
maxCardinality</a></i></li>
|
|
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#cardinalityFull">
|
|
cardinality</a></i></li>
|
|
</ul>
|
|
</td>
|
|
|
|
<td class="index" valign="top">
|
|
<b>Filler Information:</b>
|
|
|
|
<ul>
|
|
<li><i><a
|
|
href="http://www.w3.org/TR/owl-features/#hasValue">hasValue</a></i></li>
|
|
</ul>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
|
|
<h2><a id="s3" name="s3"></a>3. Language Description of OWL
|
|
Lite</h2>
|
|
|
|
<p>This section provides an informal description of the OWL
|
|
Lite language features. We do not discuss the specific syntax
|
|
of these features (see the <a
|
|
href="http://www.w3.org/TR/owl-ref/">OWL Reference</a> for
|
|
definitions). Each language feature is hyperlinked to the
|
|
appropriate place in the <a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/">OWL
|
|
Guide</a> for more examples and guidance on usage.</p>
|
|
|
|
<p>OWL Lite uses only some of the OWL language features and has
|
|
has more limitations on the use of the features than OWL DL or
|
|
OWL Full. ... are also only allowed between named classes, ...
|
|
Similarly, restrictions In OWL Lite classes can only be defined
|
|
in terms of named superclasses (superclasses cannot be
|
|
arbitrary expressions), and only certain kinds of class
|
|
restrictions can be used. Equivalence between classes and
|
|
subclass relationships between classes are also only allowed
|
|
between named classes, and not between arbitrary class
|
|
expressions. Similarly, restrictions in OWL Lite use only named
|
|
classes. OWL Lite also has a limited notion of cardinality -
|
|
the only cardinalities allowed to be explicitly stated are 0 or
|
|
1.</p>
|
|
|
|
<h3><a id="s3.1" name="s3.1"></a>3.1 OWL Lite RDF Schema
|
|
Features</h3>
|
|
<!-- FvH: now obsolete because of term glossary in Guide
|
|
This document uses the term "individual"
|
|
to refer
|
|
to objects that belong to classes (e.g., the individual Deborah belongs to the
|
|
class Person) as well as to objects that are datatypes (e.g., the individual 4
|
|
is an integer).
|
|
-->
|
|
|
|
<p>The following OWL Lite features related to RDF Schema are
|
|
included.</p>
|
|
|
|
<ul>
|
|
<li><b><i><a id="Class" name="Class"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_Class">
|
|
Class</a></i></b>: A class defines a group of individuals
|
|
that belong together because they share some properties. For
|
|
example, Deborah and Frank are both members of the class
|
|
Person. Classes can be organized in a specialization
|
|
hierarchy using <a
|
|
href="http://www.w3.org/TR/owl-features/"><i>SubClassOf</i></a>.
|
|
There is a built-in most general class named Thing that is
|
|
the class of all individuals and a superclass of all OWL
|
|
classes.</li>
|
|
|
|
<li><b><i><a id="subClassOf" name="subClassOf"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#rdfs_subClassOf">
|
|
rdfs:subClassOf</a></i></b>: Class hierarchies may be created
|
|
by making one or more statements that a class is a subclass
|
|
of another class. For example, the class Person could be
|
|
stated to be a subclass of the class Mammal. From this a
|
|
reasoner can deduce that if an individual is a Person, then
|
|
it is a Mammal.</li>
|
|
|
|
<li><b><i><a id="property" name="property"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#rdf_Property">
|
|
rdfs:Property</a></i></b>: Properties can be used to state
|
|
relationships between individuals or from individuals to data
|
|
values. Examples of properties include hasChild, hasRelative,
|
|
hasSibling, and hasAge. The first three can be used to relate
|
|
an instance of a class Person to another instance of the
|
|
class Person (and are thus ObjectProperties), and the last
|
|
(hasAge) can be used to relate an instance of the class
|
|
Person to an instance of the datatype Integer (and is thus a
|
|
Datatype property).</li>
|
|
|
|
<li><b><i><a id="subPropertyOf" name="subPropertyOf"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#rdfs_subPropertyOf">
|
|
rdfs:subPropertyOf</a></i></b>: Property hierarchies may be
|
|
created by making one or more statements that a property is a
|
|
subproperty of one or more other properties. For example,
|
|
hasSibling may be stated to be a subproperty of hasRelative.
|
|
From this a reasoner can deduce that if an individual is
|
|
related to another by the hasSibling property, then it is
|
|
also related to the other by the hasRelative property.</li>
|
|
|
|
<li><b><i><a id="domain" name="domain"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#term_domain">
|
|
rdfs:domain</a></i></b>: A domain of a property limits the
|
|
individuals to which the property can be applied. If a
|
|
property relates individual to another individual, and the
|
|
property has a class as one of its domains, then the
|
|
individual must belong to the class. For example, the
|
|
property hasChild may be stated to have the domain of Mammal.
|
|
From this a reasoner can deduce that if Frank hasChild Anna,
|
|
then Frank must be a Mammal. Note that <i>rdfs:domain</i> is
|
|
called a global restriction since the restriction is stated
|
|
on the property and not just on the property when it is
|
|
associated with a particular class. See the discussion below
|
|
on local restrictions for more information.</li>
|
|
|
|
<li><b><i><a id="range" name="range"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#term_range">
|
|
rdfs:range</a></i></b>: The range of a property limits the
|
|
individuals that the property may have as its value. If a
|
|
property relates an individual to another individual, and the
|
|
property has a class as its range, then the other indivual
|
|
must belong to the range class. For example, the property
|
|
hasChild may be stated to have the range of Mammal. From this
|
|
a reasoner can deduce that if Louise is related to Deborah by
|
|
the hasChild property, i.e., Deborah is the child of Louise,
|
|
then Deborah is a Mammal. Range is also a global restriction
|
|
as is domain above. Again, see the discussion below on local
|
|
restrictions (e.g. <a
|
|
href="http://www.w3.org/TR/owl-features/">AllValuesFrom</a>)
|
|
for more information.</li>
|
|
|
|
<li><b><i><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#term_individual">
|
|
Individual</a><a id="Individual"
|
|
name="Individual"></a></i></b> : Individuals are instances of
|
|
classes, and properties may be used to relate one individual
|
|
to another. For example, an individual named Deborah may be
|
|
described as an instance of the class Person and the property
|
|
hasEmployer may be used to relate the individual Deborah to
|
|
the individual StanfordUniversity.</li>
|
|
</ul>
|
|
|
|
<h3><a id="s3.2" name="s3.2"></a>3.2 OWL Lite Equality and
|
|
Inequality</h3>
|
|
The following OWL Lite features are related to equality or
|
|
inequality.
|
|
|
|
<ul>
|
|
<li><b><i><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_equivalentClass">
|
|
equivalentClass</a><a id="equivalentClass"
|
|
name="equivalentClass"></a></i></b> : Two classes may be
|
|
stated to be equivalent. Equivalent classes have the same
|
|
instances. Equality can be used to create synonymous classes.
|
|
For example, Car can be stated to be <i>equivalentClass</i>
|
|
to Automobile. From this a reasoner can deduce that any
|
|
individual that is an instance of Car is also an instance of
|
|
Automobile and vice versa.</li>
|
|
|
|
<li><b><i><a id="equivalentProperty"
|
|
name="equivalentProperty"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_equivalentProperty">
|
|
equivalentProperty</a></i></b>: Two properties may be stated
|
|
to be equivalent. Equivalent properties relate one individual
|
|
to the same set of other individuals. Equality may be used to
|
|
create synonymous properties. For example, hasLeader may be
|
|
stated to be the <i>equivalentProperty</i> to hasHead. From
|
|
this a reasoner can deduce that if X is related to Y by the
|
|
property hasLeader, X is also related to Y by the property
|
|
hasHead and vice versa. A reasoner can also deduce that
|
|
hasLeader is a subproperty of hasHead and hasHead is a
|
|
subProperty of hasLeader.</li>
|
|
|
|
<li><b><i><a id="sameIndividualAs"
|
|
name="sameIndividualAs"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_sameIndividualAs">
|
|
sameIndividualAs</a></i></b>: Two individuals may be stated
|
|
to be the same. This construct may be used to create a number
|
|
of different names that refer to the same individual. For
|
|
example, the individual Deborah may be stated to be the same
|
|
individual as DeborahMcGuinness.</li>
|
|
|
|
<li><b><i><a id="differentFrom" name="differentFrom"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#differentFrom">
|
|
differentFrom</a></i></b>: An individual may be stated to be
|
|
different from other individuals. For example, the individual
|
|
Frank may be stated to be different from the individuals
|
|
Deborah and Jim. Thus, if the individuals Frank and Deborah
|
|
are both values for a property that is stated to be
|
|
functional (thus the property has at most one value), then
|
|
there is a contradiction. Explicitly stating that individuals
|
|
are different can be important in when using languages such
|
|
as OWL (and RDF) that do not assume that individuals have one
|
|
and only one name. For example, with no additional
|
|
information, a reasoner will not deduce that Frank and
|
|
Deborah refer to distinct individuals.</li>
|
|
|
|
<li><b><i><a id="allDifferent" name="allDifferent"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_AllDifferent">
|
|
allDifferent</a></i></b>: A number of individuals may be
|
|
stated to be mutually distinct in one allDifferent statement.
|
|
For example, Frank, Deborah, and Jim could be stated to be
|
|
mutually distinct using the allDifferent construct. Unlike
|
|
the differentFrom statement above, this would also enforce
|
|
that Jim and Deborah are distinct (not just that Frank is
|
|
distinct from Deborah and Frank is distinct from Jim). The
|
|
allDifferent construct is particularly useful when there are
|
|
sets of distinct objects and when modelers are interested in
|
|
enforcing the unique names assumption within those sets of
|
|
objects.</li>
|
|
</ul>
|
|
|
|
<h3><a id="s3.3" name="s3.3"></a>3.3 OWL Lite Property
|
|
Characteristics</h3>
|
|
There are special identifiers in OWL Lite that are used to
|
|
provide information concerning properties and their values.
|
|
|
|
<ul>
|
|
<li><b><i><a id="inverseOf" name="inverseOf"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_inverseOf">
|
|
inverseOf</a></i></b>: One property may be stated to be the
|
|
inverse of another property. If the property P1 is stated to
|
|
be the inverse of the property P2, then if X is related to Y
|
|
by the P2 property, then Y is related to X by the P1
|
|
property. For example, if hasChild is the inverse of
|
|
hasParent and Deborah hasParent Louise, then a reasoner can
|
|
deduce that Louise hasChild Deborah.</li>
|
|
|
|
<li><b><i><a id="TransitiveProperty"
|
|
name="TransitiveProperty"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_TransitiveProperty">
|
|
TransitiveProperty</a></i></b>: Properties may be stated to
|
|
be transitive. If a property is transitive, then if the pair
|
|
(x,y) is an instance of the transitive property P, and the
|
|
pair (y,z) is an instance of P, then the pair (x,z) is also
|
|
an instance of P. For example, if ancestor is stated to be
|
|
transitive, and if Sara is an ancestor of Louise (i.e.,
|
|
(Sara,Louise) is an instance of the property ancestor) and
|
|
Louise is an ancestor of Deborah (i.e., (Louise,Deborah) is
|
|
an instance of the property ancestor), then a reasoner can
|
|
deduce that Sara is an ancestor of Deborah (i.e.,
|
|
(Sara,Deborah) is an instance of the property
|
|
ancestor).<br />
|
|
OWL Lite (and OWL DL) impose the side condition that
|
|
transitive properties (and their superproperties) cannot have
|
|
a maxCardinality 1 restriction. Without this side-condition,
|
|
OWL Lite and OWL DL would become undecidable languages. See
|
|
the property axiom section of the <a
|
|
href="http://www.w3.org/TR/owl-absyn/">OWL Abstract Syntax
|
|
and Semantics</a> document for more information.</li>
|
|
|
|
<li><b><i><a id="SymmetricProperty"
|
|
name="SymmetricProperty"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_SymmetricProperty">
|
|
SymmetricProperty</a></i></b>: Properties may be stated to be
|
|
symmetric. If a property is symmetric, then if the pair (x,y)
|
|
is an instance of the symmetric property P, then the pair
|
|
(y,x) is also an instance of P. For example, friend may be
|
|
stated to be a symmetric property. Then a reasoner that is
|
|
given that Frank is a friend of Deborah can deduce that
|
|
Deborah is a friend of Frank. Note that properties that are
|
|
to be made symmetric may not have arbitrary domains and
|
|
ranges.</li>
|
|
|
|
<li><b><i><a id="FunctionalProperty"
|
|
name="FunctionalProperty"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_FunctionalProperty">
|
|
FunctionalProperty</a></i></b> : Properties may be stated to
|
|
have a unique value. If a property is a FunctionalProperty,
|
|
then it has no more than one value for each individual (it
|
|
may have no values for an individual). This characteristic
|
|
has been referred to as having a unique property.
|
|
FunctionalProperty is shorthand for stating that the
|
|
property's minimum cardinality is zero and its maximum
|
|
cardinality is 1. For example, hasPrimaryEmployer may be
|
|
stated to be a FunctionalProperty. From this a reasoner may
|
|
deduce that no individual may have more than one primary
|
|
employer. This does not imply that every Person must have at
|
|
least one primary employer however.</li>
|
|
|
|
<li><b><i><a id="InverseFunctionalProperty"
|
|
name="InverseFunctionalProperty"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_InverseFunctionalProperty">
|
|
InverseFunctionalProperty</a></i></b>: Properties may be
|
|
stated to be inverse functional. If a property is inverse
|
|
functional then the inverse of the property is functional.
|
|
Thus the inverse of the property has at most one value for
|
|
each individual. This characteristic has also been referred
|
|
to as an unambiguous property. For example,
|
|
hasUSSocialSecurityNumber (a unique identifier for United
|
|
States residents) may be stated to be inverse functional (or
|
|
unambiguous). The inverse of this property (which may be
|
|
referred to as isTheSocialSecurityNumberFor) has at most one
|
|
value for any individual in the class of social security
|
|
numbers. Thus any one person's social security number is the
|
|
only value for their isTheSocialSecurityNumberfor property.
|
|
From this a reasoner can deduce that no two different
|
|
individual instances of Person have the identical US Social
|
|
Security Number. Also, a reasoner can deduce that if two
|
|
instances of Person have the same social security number,
|
|
then those two instances refer to the same individual.</li>
|
|
</ul>
|
|
|
|
<h3><a id="s3.4" name="s3.4"></a>3.4 OWL Lite Property Type
|
|
Restriction</h3>
|
|
OWL Lite allows restrictions to be placed on how properties can
|
|
be used by instances of a class. The following two restrictions
|
|
limit which values can be used while the next section's
|
|
restrictions limit how many values can be used.
|
|
|
|
<ul>
|
|
<li><b><i><a id="allValuesFrom" name="allValuesFrom"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_allValuesFrom">
|
|
allValuesFrom</a></i></b>: The restriction allValuesFrom is
|
|
stated on a property with respect to a class. It means that
|
|
this property on this particular class has a local range
|
|
restriction associated with it. Thus if an instance of the
|
|
class is related by the property to a second individual, then
|
|
the second individual can be inferred to be an instance of
|
|
the local range restriction class. For example, the class
|
|
Person may have a property called hasOffspring restricted to
|
|
have allValuesFrom the class Person. This means that if an
|
|
individual person Louise is related by the property
|
|
hasOffspring to the individual Deborah, then from this a
|
|
reasoner can deduce that Deborah is an instance of the class
|
|
Person. This restriction allows the property hasOffspring to
|
|
be used with other classes, such as the class Cat, and have
|
|
an appropriate value restriction associated with the use of
|
|
the property on that class. In this case, hasOffspring would
|
|
have the local range restriction of Cat when associated with
|
|
the class Cat and would have the local range restriction
|
|
Person when associated with the class Person. Note that a
|
|
reasoner can not deduce from an allValuesFrom restriction
|
|
alone that there actually is at least one value for the
|
|
property.</li>
|
|
|
|
<li><b><i><a id="someValuesFrom" name="someValuesFrom"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_someValuesFrom">
|
|
someValuesFrom</a></i></b>: The restriction
|
|
<i>someValuesFrom</i> is stated on a property with respect to
|
|
a class. A particular class may have a restriction on a
|
|
property that at least one value for that property is of a
|
|
certain type. For example, the class SemanticWebPaper may
|
|
have a <i>someValuesFrom</i> restriction on the hasKeyword
|
|
property that states that <u>some</u> value for the
|
|
hasKeyword property should be an instance of the class
|
|
SemanticWebTopic. This allows for the option of having
|
|
multiple keywords and as long as one or more is an instance
|
|
of the class SemanticWebTopic, then the paper would be
|
|
consistent with the <i>someValuesFrom</i> restriction. Unlike
|
|
<i>allValuesFrom</i>, <i>someValuesFrom</i> does not restrict
|
|
all the values of the property to be instances of the same
|
|
class. If myPaper is an instance of the SemanticWebPaper
|
|
class, then myPaper is related by the <i>hasKeyword</i>
|
|
property to at least one instance of the SemanticWebTopic
|
|
class. Note that a reasoner can not deduce (as it could with
|
|
<i>allValuesFrom</i> restrictions) that <u>all</u> values of
|
|
hasKeyword are instances of the SemanticWebTopic class</li>
|
|
</ul>
|
|
|
|
<h3><a id="s3.5" name="s3.5"></a>3.5 OWL Lite Restricted
|
|
Cardinality</h3>
|
|
|
|
<p>OWL Lite includes a limited form of cardinality
|
|
restrictions. OWL (and OWL Lite) cardinality restrictions are
|
|
referred to as local restrictions, since they are stated on
|
|
properties with respect to a particular class. That is, the
|
|
restrictions constrain the cardinality of that property on
|
|
instances of that class. OWL Lite cardinality restrictions are
|
|
limited because they only allow statements concerning
|
|
cardinalities of value 0 or 1 (they do not allow arbitrary
|
|
values for cardinality, as is the case in OWL DL and OWL
|
|
Full).</p>
|
|
|
|
<ul>
|
|
<li><b><i><a id="minCardinality" name="minCardinality"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_minCardinality">
|
|
minCardinality</a></i></b>: Cardinality is stated on a
|
|
property with respect to a particular class. If a
|
|
<i>minCardinality</i> of 1 is stated on a property with
|
|
respect to a class, then any instance of that class will be
|
|
related to at least one individual by that property. This
|
|
restriction is another way of saying that the property is
|
|
<u>required</u> to have a value for all instances of the
|
|
class. For example, the class Person would not have any
|
|
minimum cardinality restrictions stated on a hasOffspring
|
|
property since not all persons have offspring. The class
|
|
Parent, however would have a minimum cardinality of 1 on the
|
|
hasOffspring property. If a reasoner knows that Louise is a
|
|
Person, then nothing can be deduced about a minimum
|
|
cardinality for her hasOffspring property. Once it is
|
|
discovered that Louise is an instance of Parent, then a
|
|
reasoner can deduce that Louise is related to at least one
|
|
individual by the hasOffspring property. From this
|
|
information alone, a reasoner can not deduce any maximum
|
|
number of offspring for individual instances of the class
|
|
parent. In OWL Lite the only minimum cardinalities allowed
|
|
are 0 or 1. A minimum cardinality of zero on a property just
|
|
states (in the absence of any more specific information) that
|
|
the property is optional with respect to a class. For
|
|
example, the property has Offspring may have a minimum
|
|
cardinality of zero on the class Person (while it is stated
|
|
to have the more specific information of minimum cardinality
|
|
of one on the class Parent).</li>
|
|
|
|
<li><b><i><a id="maxCardinality" name="maxCardinality"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_maxCardinality">
|
|
maxCardinality</a></i></b>: Cardinality is stated on a
|
|
property with respect to a particular class. If a
|
|
<i>maxCardinality</i> of 1 is stated on a property with
|
|
respect to a class, then any instance of that class will be
|
|
related to at most one individual by that property. A
|
|
maxCardinality 1 restriction is sometimes called a functional
|
|
or unique property. For example, the property
|
|
hasRegisteredVotingState on the class UnitedStatesCitizens
|
|
may have a maximum cardinality of one (because people are
|
|
only allowed to vote in only one state). From this a reasoner
|
|
can deduce that individual instances of the class USCitizens
|
|
may not be related to two or more distinct individuals
|
|
through the hasRegisteredVotingState property. From a maximum
|
|
cardinality one restriction alone, a reasoner can not deduce
|
|
a minimum cardinality of 1. It may be useful to state that
|
|
certain classes have no values for a particular property. For
|
|
example, instances of the class UnmarriedPerson should not be
|
|
related to <u>any</u> individuals by the property hasSpouse.
|
|
This situation is represented by a maximum cardinality of
|
|
zero on the hasSpouse property on the class
|
|
UnmarriedPerson.</li>
|
|
|
|
<li><b><i><a id="Cardinality" name="Cardinality"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_cardinality">
|
|
cardinality</a></i></b>: Cardinality is provided as a
|
|
convenience when it is useful to state that a property on a
|
|
class has both <i>minCardinality</i> 0 and
|
|
<i>maxCardinality</i> 0 or both <i>minCardinality</i> 1 and
|
|
<i>maxCardinality</i> 1. For example, the class Person has
|
|
exactly one value for the property hasBirthMother. From this
|
|
a reasoner can deduce that no two distinct individual
|
|
instances of the class Mother may be values for the
|
|
hasBirthMother property of the same person.</li>
|
|
</ul>
|
|
Alternate namings for these restricted forms of cardinality
|
|
were discussed. Current recommendations are to include any such
|
|
names in a front end system. More on this topic is available on
|
|
the publically available webont mail archives with the most
|
|
relevant message at <a
|
|
href="http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0063.html">
|
|
http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0063.html</a>.
|
|
|
|
|
|
<h3><a id="s3.6" name="s3.6"></a>3.6 OWL Lite Class
|
|
Intersection</h3>
|
|
OWL Lite has contains an intersection constructor but limits
|
|
its usage. <!--(OWL full does not place limitations
|
|
on the use of boolean constructors such as intersection.)
|
|
-->
|
|
|
|
<ul>
|
|
<li><b><i><a id="intersectionOf" name="intersectionOf"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_intersectionOf">
|
|
intersectionOf</a></i></b>: OWL Lite allows intersections of
|
|
named classes and restrictions. For example, the class
|
|
EmployedPerson can be described as the <i>intersectionOf</i>
|
|
Person and EmployedThings (which could be defined as things
|
|
that have a minimum cardinality of 1 on the hasEmployer
|
|
property). From this a reasoner may deduce that any
|
|
particular EmployedPerson has at least one employer.
|
|
<!-- OWL Lite requires <i>intersectionOf</i> to take named
|
|
classes thus it would not be allowed in OWL Lite to
|
|
describe EmployedPerson as the intersection of Person
|
|
and the unnamed the class of things that have at
|
|
least one employer and is simultaneously an instance
|
|
of the class Person.
|
|
The ability to use unnamed classes is introduced in
|
|
OWL DL and OWL Full.
|
|
--></li>
|
|
</ul>
|
|
|
|
<h3><a id="s3.7" name="s3.7"></a>3.7 Datatypes</h3>
|
|
|
|
<p>OWL uses the RDF mechanisms for data values.
|
|
<!-- dlm: removed with suggestion from pfps. too much detail.
|
|
datatyping scheme, which provides a mechanism for referring to pointer
|
|
href="http://www.daml.org/2002/06/webont/owl-ref-proposed#ref-xml-schema2">XML
|
|
Schema datatypes</A>. Such XML Schema datatypes are identified by a URI, and
|
|
each time an instance of such a datatype occurs, it must have an RDF attribute
|
|
rdf:datatype whose value should be the URI reference of the XML Schema datatype.
|
|
-->See the <a
|
|
href="http://www.daml.org/2002/06/webont/owl-ref-proposed#rdf-datatype">
|
|
OWL Guide</a> for a more detailed description.</p>
|
|
|
|
<h3><a id="s3.8" name="s3.8"></a>3.8 OWL Lite Header
|
|
Information</h3>
|
|
OWL Lite supports notions of ontology inclusion and
|
|
relationships and attaching information to ontologies.
|
|
<!-- dlm: removed specificity of section previously included
|
|
OWL supports
|
|
standard notions of ontology referencing, inclusion, and meta-information. All
|
|
three levels of OWL include ways of specifying ontologies to import, ontology
|
|
version information, prior ontology version information, ontologies known to be
|
|
backward compatible, and ontologies known to be incompatible.
|
|
-->
|
|
See the <a href="http://www.w3.org/TR/owl-ref/#">OWL
|
|
Reference</a> for details and the <a
|
|
href="http://www.w3.org/TR/owl-guide/">OWL Guide</a> for
|
|
examples.
|
|
|
|
<h2><a id="s4" name="s4"></a>4. Incremental Language
|
|
Description of OWL DL and OWL FULL</h2>
|
|
Both OWL DL and OWL Full use the same vocabulary although OWL
|
|
DL is subject to some restrictions. Roughly, OWL DL requires
|
|
type separation (a class can not also be an individual or
|
|
property, a property can not also be an individual or class).
|
|
This implies that restrictions cannot be applied to the
|
|
language elements of OWL itself (something that is allowed in
|
|
OWL Full). Furthermore, OWL DL requires that properties are
|
|
either ObjectProperties or DatatypeProperties:
|
|
DatatypeProperties are relations between instances of classes
|
|
and RDF literals and XML Schema datatypes, while
|
|
ObjectProperties are relations between instances of two
|
|
classes. The <a href="http://www.w3.org/TR/owl-absyn/">OWL
|
|
Abstract Syntax and Semantics</a> document explains the
|
|
distinctions and limitations. We describe the OWL DL and OWL
|
|
Full vocabulary that extends the constructions of OWL Lite
|
|
below.
|
|
|
|
<ul>
|
|
<li><b><i><a id="oneOf" name="oneOf"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_oneOf">
|
|
oneOf</a></i></b>: (enumerated classes): Classes can be
|
|
described by enumeration of the individuals that make up the
|
|
class. The members of the class are exactly the set of
|
|
enumerated individuals; no more, no less. For example, the
|
|
class of daysOfTheWeek can be described by simply enumerating
|
|
the individuals Sunday, Monday, Tuesday, Wednesday, Thursday,
|
|
Friday, Saturday. From this a reasoner can deduce the maximum
|
|
cardinality (7) of any property that has daysOfTheWeek as its
|
|
allValuesFrom restriction.</li>
|
|
|
|
<li><b><i><a id="hasValue" name="hasValue"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_hasValue">
|
|
hasValue</a></i></b>: (property values): A property can be
|
|
required to have a certain individual as a value (also
|
|
sometimes referred to as property values). For example,
|
|
instances of the class of dutchCitizens can be characterized
|
|
as those people that have theNetherlands as a value of their
|
|
nationality. (TheNetherlands itself is an instance of the
|
|
class of Nationalities).</li>
|
|
|
|
<li><b><i><a id="disjointWith" name="disjointWith"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_disjointWith">
|
|
disjointWith</a></i></b>: OWL Full allows the statement that
|
|
classes are disjoint. For example, Man and Woman can be
|
|
stated to be disjoint classes. From this disjointWith
|
|
statement, a reasoner can deduce an inconsistency when an
|
|
individual is stated to be an instance of both and similarly
|
|
a reasoner can deduce that if A is an instance of Man, then A
|
|
is <i>not</i> an instance of Woman.</li>
|
|
|
|
<li><b><i><a id="booleanFull" name="booleanFull"></a><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_unionOf">
|
|
unionOf, complementOf, intersectionOf</a></i></b> (Boolean
|
|
combinations): OWL allows arbitrary Boolean combinations of
|
|
classes and restrictions: unionOf, complementOf, and
|
|
intersectionOf. For example, using unionOf, we can state that
|
|
a class contains things that are either USCitizens or
|
|
DutchCitizens. Using complementOf, we could state that
|
|
children are <i>not</i> SeniorCitizens. (i.e. the class
|
|
Children is a subclass of the complement of SeniorCitizens).
|
|
Citizenship of the European Union could be described as the
|
|
union of the citizenship of all member states.</li>
|
|
|
|
<li><b><i><a
|
|
href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/#owl_cardinality">
|
|
minCardinality, maxCardinality, cardinality</a><a
|
|
id="cardinalityFull" name="cardinalityFull"></a></i></b>
|
|
(full cardinality): While in OWL Lite, cardinalities are
|
|
restricted to at least, at most or exactly 1 or 0, full OWL
|
|
allows cardinality statements for arbitrary non-negative
|
|
integers. For example the class of DINKs ("Dual Income, No
|
|
Kids") would restrict the cardinality of the property
|
|
hasIncome to a minimum cardinality of two (while the property
|
|
hasChild would have be restricted to cardinality 0).</li>
|
|
|
|
<li><b><i><a id="complexClassFull"
|
|
name="complexClassFull">complex classes</a></i></b> : In many
|
|
constructs, OWL Lite restricts the syntax to single class
|
|
names (e.g. in subClassOf or equivalentClass statements). OWL
|
|
Full extends this restriction to allow arbitrarily complex
|
|
class descriptions, consisting of enumerated classes,
|
|
property restrictions, and Boolean combinations. OWL also
|
|
includes a special "bottom" class with the name Nothing that
|
|
is the class that has no instances. Also, OWL full allows
|
|
classes to be used as instances (and OWL DL and OWL Lite do
|
|
not). For more on this topic, see the "Design for Use"
|
|
section of the Guide document.</li>
|
|
</ul>
|
|
|
|
<h2><a id="s5" name="s5">5. Summary</a></h2>
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This document provides an overview of the Web Ontology Language
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by providing a brief introduction to why one might need a Web
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ontology language and how OWL fits in with related W3C
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languages. It also provides a brief description of the three
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OWL sublanguages: OWL Lite, OWL DL, and OWL Full along with a
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feature synopsis for each of the languages. This document is an
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update to the Feature Synopsis Document. It provides simple
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descriptions of the constructs along with simple examples. It
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references the <a href="http://www.w3.org/TR/owl-ref/">OWL
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reference document</a>, the <a
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href="http://www.w3.org/TR/2003/WD-owl-guide-20030210/">OWL
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|
Guide</a>, and the <a
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href="http://www.w3.org/TR/owl-absyn/">OWL Abstract Syntax and
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Semantics</a> document for more details. Previous versions (<a
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href="http://www.ksl.stanford.edu/people/dlm/webont/OWLFeatureSynopsisJan22003.htm">
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January 2, 2003</a>, <a
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href="http://www.ksl.stanford.edu/people/dlm/webont/OWLFeatureSynopsisJuly29.htm">
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July 29, 2002</a>, <a
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|
href="http://www.ksl.stanford.edu/people/dlm/webont/OWLFeatureSynopsisJuly8.htm">
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July 8, 2002</a>, <a
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href="http://www.ksl.stanford.edu/people/dlm/webont/OWLFeatureSynopsisJune23.htm">
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June 23, 2002</a>, <a
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href="http://www.ksl.stanford.edu/people/dlm/webont/complianceMay262002.html">
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May 26, 2002</a>, and <a
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href="http://www.ksl.stanford.edu/people/dlm/webont/complianceMay152002.html">
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May 15, 2002</a>) of this document provide the historical view
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of the evolution of OWL Lite and the issues discussed in its
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evolution.
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<h2><a id="s6" name="s6">Acknowledgements</a></h2>
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This document is the result of extensive discussions within the
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Web Ontology Working Group as a whole. The members of this
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working group were Jean-François Baget, James Barnette,
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Sean Bechhofer, Jonathan Borden, Frederik Brysse, Stephen
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Buswell, Peter Crowther, Jos De Roo, David De Roure, Mike Dean,
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Larry Eshelman, Jérôme Euzenat, Dieter Fensel, Tim
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Finin, Nicholas Gibbins, Pat Hayes, Jeff Heflin, Ziv Hellman,
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James Hendler, Bernard Horan, Masahiro Hori, Ian Horrocks,
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Francesco Iannuzzelli, Mario Jeckle, Ruediger Klein, Ora
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Lassila, Alexander Maedche, Massimo Marchiori, Deborah
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McGuinness, Libby Miller, Enrico Motta, Leo Obrst, Laurent
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Olivry , Peter Patel-Schneider, Martin Pike, Marwan Sabbouh,
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Guus Schreiber, Noboru Shimizu, Michael Sintek, Michael Smith,
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Ned Smith, John Stanton, Lynn Andrea Stein, Herman ter Horst,
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Lynne R. Thompson, David Trastour, Frank van Harmelen, Raphael
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Volz, Evan Wallace, Christopher Welty, and John Yanosy.
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</body>
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