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<title>Report from the W3C Workshop on RDF Access to Relational Databases</title>
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<p><a href="/"><img border="0" src="/Icons/WWW/w3c_home" alt="W3C" /></a> <a href="/TandS/"><img src="/Icons/tands.gif" alt="Technology and Society Domain" width="212" height="48" border="0" /></a> <a href="/2001/sw/"><img src="/2001/sw/sw" alt="The Semantic Web Home Page" border="0" /></a></p>
<div class="head">
<h1 class="subtitle no-toc" id="report">Report from the W3C Workshop on<br />
RDF Access to Relational Databases</h1>
<p style="text-align: center" id="navbar"><a href=".">RdfRDB Workshop</a> • <a href="program">Program</a> • <a href="report">Workshop Report</a> • <a href="minutes">Meeting Minutes</a> • <a href="cfp">Call For Participation</a> • <a href="accepted">Accepted Papers</a></p>
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<h2>Status</h2>
<p>This report is potentially final. Comments are welcome at <a href="mailto:RdfRDB-chairs@w3.org">RdfRDB-chairs@w3.org</a>.</p>
<div class="abstract">
<p><strong>Summary:</strong></p>
<p>In October 2007, the W3C held a two-day workshop to explore current and emerging technologies for RDF Access to Relational Databases. Sixty four representatives from twenty two organizations, including Semantic Web users, tool vendors, and academics, gather to present use cases and technologies.</p>
<p>Presentations exposed user needs and developer technologies. Participants expressed a desire to continute to develop these technologies in an <a href="/2005/Incubator/procedures.html">Incubator Group</a> context. Two areas of continued work were selected:</p>
<ul>
<li id="defn_mapping"><em>Mapping</em> — the rules for converting tuples and relationships in a relational database to nodes and arcs in RDF.</li>
<li id="defn_benchmarks"><em>Benchmarks</em> — a set of tests and protocols (test plans) to compare the speed and resource impact of expressing relational data as RDF.</li>
</ul>
<p>Query federation (distributing portions of a query over different databases) was also deemed important, but was tightly enough bound to mapping that federation work should be done in a mapping incubator group. Technical mail about query relational databases with SPARQL should go to <a href="mailto:public-sparql-dev@w3.org"></a> and other technical mail should go to the the RDF Interest Group <a href="mailto:semantic-web@w3.org">semantic-web@w3.org</a>.</p>
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<div class="map">
<p><strong>Contents:</strong></p>
<ul class="toc">
<li><a href="#introduction"><span class="secno">1.</span> Introduction</a></li>
<li><a href="#needs"><span class="secno">2.</span> User Needs</a></li>
<li><a href="#impls"><span class="secno">3.</span> Implemented Technologies</a></li>
<li><a href="#conclusions"><span class="secno">4.</span> Future Work</a></li>
</ul>
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<h2 id="introduction"><span class="secno">1.</span> <a id="C"
name="C">Introduction</a></h2>
<p>Semantic Web developers have been focusing on ways to express conventional relational data as RDF. The ubiquity of machine-processable relational data makes it an attractive source of Semantic Web data. RDF's grounding in universal terms makes RDF attractive to the relational database community. Many Semantic Web systems in current development provide this utility, either through projection of relational data into triples or through translating Semantic Web queries into SQL.</p>
<p>On 25 and 26 October, 2007, the W3C held a workshop in Cambridge, Massachusetts, to gather information about standards work in this area. The <a href="cfp">Call for Participation</a> was <a href="http://lists.w3.org/Archives/Public/semantic-web/2005Feb/0099.html">@@issued@@</a> on 20 July, 2007. It covered the background and goals of the workshop, and invited parties interested in attending to submit position papers.</p>
<p>After review, the program committee accepted <a href="accepted">18 papers</a> and selected a subset of them for presentation, as listed in <a href="program">the program.</a> <a href="registered">64 people</a> attended, representing a wide range of interest. W3C is grateful to <a href="http://www.novartis.com/">Novartis</a> for hosting the workshop.</p>
<h2 id="needs"><span class="secno">2.</span> User Needs</h2>
<p>Use cases from <a href="program#compSci2">Verizon</a>, <a href="program#UltraLink">Novartis</a>, <a href="program#squirrel">HP</a>, <a href="program#ucb">UCB Group</a> and the <a href="program#epa">EPA</a> provided a context for evaluating the <a href="#impls">presented technologies</a>. They discussed a variety of architectural needs. </p>
<p><a href="program#enterpriseRDB">Boeing</a>, and <a href="program#oracle">Oracle</a> explored mapping potential at a meta-level. <a href='program#generalmapping"'>Vipul Kashyap</a> made a case for treating relational mappings as a specific case of general RDF mappings. <a href="program#SPARQLtests">Matthew Gheen</a> mapped SPARQL tests to run over relations created with SQL DDL.</p>
<h2 id="impls"><span class="secno">3.</span> Implemented Technologies</h2>
<p><a href="program#squirrel">SquirrelRDF</a> and <a href="program#d2r">D2RQ</a> use rules to map SPARQL to SQL. The <a href="program#virtuoso">Virtuoso</a> database creates a virtual triple store, over which SPARQL queries can be run.</p>
<p>All of these technologies require specific mappings from relational schemas to RDF graphs. <a href="program#DDL2RDF">Work at the University of Texas at Austin</a> automates the process. <a href="program#SPIDERS">Telefonica I+D's</a> SPIDERS project provides a Protegé plugin to help users with the mapping.</p>
<p><a href="program#semSitemap">Semantic Sitemaps</a> provide metadata for query direction/federation.</p>
<h2 id="conclusions"><span class="secno">4.</span> Future Work</h2>
<p>During the <a>wrap-up discussion</a>, participants re-evaluated the products of the <a>break-out sesssion</a> in the context of future work. Around 15 participants volunteered to start and develop <a href="../../2005/Incubator/procedures">W3C Incubator Groups</a> to standardize data/query mapping and query federation as well as establish a set of benchmarks for comparing different tools. Implementor's current tools met a subset of the users' needs and the expectation was that further development and standardization would be well worth the effort.</p>
<p>Two Incubator Groups (XGs) will be chartered:</p>
<ul>
<li><a href="#defn_mapping">Mapping</a> — develop standards for expressing mappings between RDF and conventional (normalized) relational databases:
<p>Query federation is considered a critical functionality for system providing query mapping functionality. However, a group examining query federation was thought to have an impractical number of dependencies on mapping so query federation issues will be addressed in the mapping XG.</p>
<p><em>Existing work</em>: <a href="program.html#d2r">D2RQ</a>, <a href="program.html#virtuoso">Virtuoso</a>,
<a href="program.html#squirrel">SquirrelRDF</a>, <a href="http://www.w3.org/2005/05/22-SPARQL-MySQL/XTech">SPASQL</a></p>
</li>
<li><a href="#defn_benchmarks">Benchmarks</a> — develop a standard set of tests for comparing functionality and performance of different mapping systems:
<p><em>Existing work</em>: <a href="program#SPARQLtests">Matthew Gheen's work</a></p>
</li>
</ul>
<p>While W3C Incubator Groups require minimal W3C Team resources, this area of work is of great interest to several members of the team and is considered crucial technology for the health of the Semantic Web. Draft charters are being written and discussed with members of the W3C Team.</p>
<div class="author">
<hr />
<a href="/People/Eric">Eric Prud'hommeaux</a><br />
<a
href="/2007/03/RdfRDB/report">http://www.w3.org/2007/03/RdfRDB/report</a>
<pre>$Id: report.html,v 1.7 2007/12/09 16:34:52 eric Exp $</pre>
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