ontology
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<h1 class="title">
<img src="/2008/site/images/theme-web-semantics" alt="" />Vocabularies</h1>
<ul class="w3c_toc">
<li class="toc_prefix">On this page → </li>
<li><a href="#summary">what is a vocabulary</a>
<span class="bullet">• </span>
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<li><a href="#uses">what are vocabularies used for</a>
<span class="bullet">• </span>
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<h2 id="summary">What is a Vocabulary?</h2>
<p>On the Semantic Web, vocabularies define the concepts and relationships (also referred to as
“terms”) used to describe and represent an area of concern. Vocabularies
are used to classify
the terms that can be used in a particular application, characterize possible relationships,
and define possible constraints on using those terms. In practice, vocabularies can be very
complex (with several thousands of terms) or very simple (describing one or two concepts
only).</p>
<p>There is no clear division between what is referred to as
“vocabularies” and “ontologies”. The trend is to
use the word “ontology” for more complex, and possibly quite formal collection of
terms, whereas “vocabulary” is used when such strict formalism is not necessarily
used or only in a very loose sense. Vocabularies are the basic building blocks
for <a href="inference">inference</a> techniques on the Semantic Web.</p>
<h2 id="uses">What are Vocabularies Used For?</h2>
<p>The role of vocabularies on the Semantic Web are to help data integration when,
for example, ambiguities may exist on the terms used in the different data sets, or when a bit
of extra knowledge may lead to the discovery of new relationships.
Consider, for example, the application of ontologies in the field of health care.
Medical professionals use
them to represent knowledge about symptoms, diseases, and treatments. Pharmaceutical companies
use them to represent information about drugs, dosages, and allergies. Combining this knowledge
from the medical and pharmaceutical communities with patient data enables a whole range of
intelligent applications such as decision support tools that search for possible treatments;
systems that monitor drug efficacy and possible side effects; and tools that support
epidemiological research.</p>
<p>Another type of example is to use vocabularies to organize knowledge. Libraries, museums,
newspapers, government portals, enterprises, social networking applications, and other
communities that manage large collections of books, historical artifacts, news reports,
business glossaries, blog entries, and other items can now use vocabularies, using
standard formalisms, to leverage the power of <a href="linkeddata">linked data</a>.</p>
<p>It depends on the application how complex vocabularies they use. Some applications
may decide not to use even small vocabularies, and rely on the logic of the application program.
Some application may choose to use very simple vocabularies like the one described in the
<a href="#examples">examples section below</a>, and let a general Semantic Web environment use
that extra information to make the identification of the terms.
Some applications need an agreement on common terminologies, without any rigor imposed by a logic system.
Finally, some applications may need more complex ontologies with complex reasoning procedures.
It all depends on the requirements and the goals of the applications.</p>
<p>To satisfy these different needs, W3C offers a large palette of techniques to describe and
define different forms of vocabularies
in a standard format. These include <a href="http://www.w3.org/standards/techs/rdf#w3c_all">RDF and RDF Schemas</a>,
<a href="http://www.w3.org/standards/techs/skos#w3c_all">Simple Knowledge Organization System (SKOS)</a>,
<a href="http://www.w3.org/standards/techs/owl#w3c_all">Web Ontology Language (OWL)</a>, and the
<a href="http://www.w3.org/standards/techs/rif#w3c_all">Rule Interchange Format (RIF)</a>.
The choice among these different
technologies depend on the complexity and rigor required by a specific application.</p>
<h2 id="examples">Examples</h2>
<p>A general example may help. A bookseller may want to integrate data coming from different publishers.
The data can be imported into a common RDF model, eg, by using converters to the publishers’
databases. However, one database may use the term “author”, whereas the other may use the
term “creator”. To make the integration complete, and extra definition should be added to the RDF data,
describing the fact that the relationship described as “author” is the same as “creator”. This
extra piece of information is, in fact, a vocabulary (or an ontology), albeit an extremely simple one.</p>
<p>In a more complex case the application may need a more detailed ontology as part of the extra
information. This
may include formal description on how authors are to be uniquely identified (eg, in a US
setting, by referring to a unique social security number), how the terms used in this particular
application relate to other datasets on the Web (eg, Wikipedia or geographic information), how
the term “author” (or “creator”) can be related to terms like
“editors”, etc.</p>
<h2 id="learnmore">Learn More</h2>
<p>The Semantic Web community maintains a <a href="http://esw.w3.org/topic/SwBooks">list of books</a>
on a W3C Wiki page. Some of those books
are introductory in nature while others are conference proceedings or
textbook that address more advanced topics.
Details of <a href="http://www.w3.org/2007/11/Talks/Semantic_Web.html">recent and upcoming
Semantic Web related talks</a>, given by the <a href="http://www.w3.org/People/">W3C Staff</a>,
the <a href="http://www.w3.org/Consortium/Offices/">staff of the W3C Offices</a>,
and members of the W3C Working Groups are available separately; the slides
are usually publicly available. The
W3C also maintains a <a href="http://www.w3.org/2001/sw/sweo/public/UseCases/">collection of Semantic
Web Case Studies and Use Cases</a> that
show how Semantic Web technologies, including vocabularies, are used in
practice. Finally, the <a href="/2001/sw/SW-FAQ">Semantic Web FAQ</a> may also be of help
in understanding the various concepts.</p>
<div id="recentpress"><!-- start generated recent press --><h2>Recent Press</h2>
<dl>
<dt>
<span class="press_date">8 December</span>
<br />
<a href="http://blog.antidot.net/">Blog Antidot</a>
</dt>
<dd>
<a href="http://blog.antidot.net/2011/12/08/grande-semaine-pour-lopen-data-francais/">
“<cite>Grande semaine pour l’Open Data français !</cite>”
</a>
</dd>
<dt>
<span class="press_date">1 December</span>
<br />
<a href="http://computerworld.co.nz/">Computer World</a>
</dt>
<dd>
<a href="http://computerworld.co.nz/news.nsf/news/ibm-develops-ideas-for-astronomically-big-data">
“<cite>IBM develops ideas for astronomically Big Data</cite>”
</a>
</dd>
<dt>
<span class="press_date">26 November</span>
<br />
<a href="http://searchenginewatch.com/">Search Engine Watch</a>
</dt>
<dd>
<a href="http://searchenginewatch.com/article/2127381/Volunia-Search-Engine-A-Radical-New-View-of-Search">
“<cite>Volunia Search Engine: A 'Radical New View' of Search</cite>”
</a>
</dd>
<dt>
<span class="press_date">22 November</span>
<br />
<a href="http://www.huffingtonpost.com/tech/">Huffpost Tech</a>
</dt>
<dd>
<a href="http://www.huffingtonpost.com/steve-hamby/top-three-technologies-to_b_1105022.html">
“<cite>Top Three Technologies to Tame the Big Data Beast</cite>”
</a>
</dd>
</dl>
<!-- end generated recent press --></div>
<h2 id="specifications">Current Status of Specifications</h2>
<p>Learn more about the current status of specifications related
to:
</p>
<div id="w3c_techs_body"><ul class="show_items"><li>
<a href="/standards/techs/rdf">RDF</a>
</li><li>
<a href="/standards/techs/owl">OWL Web Ontology Language</a>
</li><li>
<a href="/standards/techs/skos">SKOS</a>
</li><li>
<a href="/standards/techs/earl">Evaluation and Report Language (EARL)</a>
</li></ul></div>
<p>These <a href="/Consortium/activities">W3C Groups</a> are
working on the related specifications:
</p>
<div id="w3c_groups"><ul class="show_items">
<li>
<a href="http://www.w3.org/2007/OWL/">OWL Working Group</a>
</li>
<li>
<a href="http://www.w3.org/2005/rules/wg.html">Rule Interchange Format Working Group</a>
</li>
<li>
<a href="http://www.w3.org/WAI/ER/">Evaluation and Repair Tools Working Group</a>
</li>
<li>
<a href="http://www.w3.org/2001/sw/interest/">Semantic Web Interest Group</a>
</li>
</ul></div>
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<h2 class="h4 category">Current Status</h2>
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<li>
<a href="/standards/techs/rdf">RDF</a>
</li>
<li>
<a href="/standards/techs/owl">OWL Web Ontology Language</a>
</li>
<li>
<a href="/standards/techs/skos">SKOS</a>
</li>
<li>
<a href="/standards/techs/earl">Evaluation and Report Language (EARL)</a>
</li>
</ul>
</div>
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<h2 class="h4 category">Use It</h2>
<ul class="theme right-list">
<li class="tutorials_link">
<a href="/2002/03/tutorials#semanticweb_ontology">Tutorials</a>
</li>
<li>Business Case</li>
<li>Software</li>
</ul>
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<h2 class="h4 category">Validators</h2>
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<li>
<a title="RDF Validator" href="http://www.w3.org/RDF/Validator/">RDF</a>
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<h2 class="h4 category">Logos</h2>
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<a href="http://www.w3.org/2007/10/sw-logos.html#sw-owl">OWL</a>
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<li>
<a href="http://www.w3.org/2007/10/sw-logos.html#sw-powder">POWDER</a>
</li>
<li>
<a href="http://www.w3.org/2007/10/sw-logos.html#sw-skos">SKOS</a>
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