http://www.openlinksw.com/GData/127/1556/2
Kingsley Idehen's Blog Data Space
2009-11-23T10:53:44Z
Kingsley Uyi Idehen
kidehen@openlinksw.com
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<p> While exploring the <a href="http://id.loc.gov/authorities/" id="link-id1488cca8">Subject Headings Linked Data Space</a> (LCSH) recently unveiled by the <a href="http://id.loc.gov/" id="link-id1672ad10">Library of Congress</a>, I noticed that the <a href="http://dbpedia.org/resource/Uniform_Resource_Identifier" id="link-id158fef78">URI</a> for the subject heading: <a href="http://id.loc.gov/authorities/sh95000541#concept" id="link-id14c8d3e8">World Wide Web</a>, exposes an "owl:sameAs" link to resource URI: "info:lc/authorities/sh95000541" -- in fact, a URI.URN that isn't HTTP protocol scheme based.</p> <p> The observations above triggered a <a href="http://search.twitter.com/search?q=&ands=&phrase=&ors=&nots=&tag=linkeddata&lang=all&from=kidehen&to=edsu&ref=&near=&within=15&units=mi&since=2009-05-01&until=2009-05-05&rpp=10" id="link-id14e21ba0">discussion thread on Twitter</a> that involved: <a href="http://twitter.com/edsu" id="link-ide411808">@edsu</a>, <a href="http://twitter.com/iand" id="link-id11915ed0">@iand</a>, and <a href="http://twitter.com/kidehen" id="link-id1519c028">moi</a>. Naturally, it morphed into a live demonstration of: human vs machine, interpretation of claims expressed in the RDF graph.</p> <h3>What makes this whole thing interesting?</h3> <p>It showcases (in Man vs Machine style) the issue of unambiguously discerning the meaning of the owl:sameAs claim expressed in the LCSH <a href="http://dbpedia.org/resource/Resource_Description_Framework" id="link-id17004728">Linked Data Space</a>.</p> <h4>Perspectives & Potential Confusion</h4> <p> From the Linked Data perspective, it may spook a few people to see owl:sameAs values such as: "info:lc/authorities/sh95000541", that cannot be de-referenced using HTTP. </p> <p> It may confuse a few people or user agents that see URI de-referencing as not necessarily HTTP specific, thereby attempting to de-reference the URI.URN on the assumption that it's associated with a "<a href="http://www.handle.net/overviews/overview.html" id="link-id155517a8">handle system</a>", for instance.</p> <p> It may even confuse RDFizer / RDFization middleware that use owl:sameAs as a <a href="http://dbpedia.org/resource/Data">data</a> provider attribution mechanism via hint/nudge URI values derived from original content / data URI.URLs that de-reference to nothing e.g., an original resource URI.<a href="http://dbpedia.org/resource/Uniform_Resource_Locator" id="link-id119e0d80">URL</a> plus "#this" which produces URI.URN-URL -- think of this pattern as "owl:shameAs" in a sense :-)</p> <h3> Unambiguously Discerning Meaning</h3> <p> Simply bring OWL reasoning (inference rules and reasoners) into the mix, thereby negating human dialogue about interpretation which ultimately unveils a mesh of orthogonal view points. Remember, OWL is all about infrastructure that ultimately enables you to express yourself clearly i.e., say what you mean, and mean what you say. </p> <h3>Path to Clarity (using <a href="http://virtuoso.openlinksw.com" id="link-id1537aa68">Virtuoso</a>, its in-built Sponger Middleware, and Inference Engine):</h3> <ol> <li>GET the data into the Virtuoso Quad store -- what the sponger does via its <a href="http://linkeddata.uriburner.com/about/html/http://id.loc.gov/authorities/sh95000541#concept" id="link-id1669fa40">URIBurner Service</a> (while following designated predicates such as owl:sameAs in case they point to other mesh-able data sources)</li> <li>Query the data in Quad Store with "owl:sameAs" inference rules enabled</li> <li>Repeat the last step with the inference rules excluded.</li> </ol> <h4>Actual <a href="http://dbpedia.org/resource/SPARQL" id="link-id17374110">SPARQL</a> Queries:</h4> <ul> <li> <a href="http://demo.openlinksw.com/DAV/home/demo/Public/Queries/DataWeb/lcsh_www_subject_heading.isparql" id="link-id16c986d0">SPARQL Query against the HTTP based Subject Heading URI for WWW</a> </li> <li> <a href="http://demo.openlinksw.com/DAV/home/demo/Public/Queries/DataWeb/lcsh_www_subject_heading_sameAs_inference_on.isparql" id="link-id16d4fea0">SPARQL Query (with reasoning via inference rule for owl:sameAs)</a> against the URN based Subject Heading URI for WWW</li> <li> <a href="http://demo.openlinksw.com/DAV/home/demo/Public/Queries/DataWeb/lcsh_www_subject_heading_no_sameAs_inference_on.isparql" id="link-id11bad768">SPARQL Query (*without* reasoning via inference rule for owl:sameAs)</a> against the URN based Subject Heading URI for WWW</li> </ul> <h4>Observations:</h4> <p> The <a href="http://dbpedia.org/resource/SPARQL" id="link-ide6acf68">SPARQL</a> queries against the Graph generated and automatically populated by the Sponger reveal -- without human intervention-- that: "info:lc/authorities/sh95000541", is just an alternative name for < xmlns="http" id.loc.gov="id.loc.gov" authorities="authorities" sh95000541="sh95000541" concept="concept">, and that the graph produced by LCSH is self-describing enough for an OWL reasoner to figure this all out courtesy of the <a href="http://linkeddata.uriburner.com/about/html/http://www.w3.org/2002/07/owl%23sameAs" id="link-id13e364b0">owl:sameAs</a> property :-).</p> <p>Hopefully, this post also provides a simple example of how <a href="http://dbpedia.org/resource/Web_Ontology_Language" id="link-id158a3fe8">OWL</a> facilitates "Reasonable Linked Data". </p> <h3>Related</h3> <ul> <li> <a href="http://www.openlinksw.com/dataspace/kidehen@openlinksw.com/weblog/kidehen@openlinksw.com%27s%20BLOG%20%5B127%5D/1455" id="link-id164e19f8">State of the Linked Data Web</a> </li> <li> <a href="http://www.mkbergman.com/?p=474" id="link-id11973d10">Making Linked Data Reasonable Using Description Logics Series</a> - post by <a href="http://community.linkeddata.org/dataspace/person/mkbergman#this" id="link-id1184bfb8">Mike Bergman</a> </li> </ul>
Library of Congress & Reasonable Linked Data
2009-05-06T18:26:15Z
2009-05-06T14:26:15.000034-04:00
Kingsley Uyi Idehen
kidehen@openlinksw.com