http://www.openlinksw.com/GData/127/1567/3
Kingsley Idehen's Blog Data Space
2009-11-23T11:17:06Z
Kingsley Uyi Idehen
kidehen@openlinksw.com
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<h3>Situation Analysis</h3> <p>As the "<a href="http://www.w3.org/DesignIssues/LinkedData.html" id="link-id12f96a00">Linked Data" meme</a> has gained momentum you've more than likely been on the receiving end of dialog with Linked Open <a href="http://dbpedia.org/resource/Data">Data</a> community members (myself included) that goes something like this:</p> <blockquote> <cite>"Do you have a <a href="http://dbpedia.org/resource/Uniform_Resource_Identifier" id="link-id139252a0">URI</a>", "Get yourself a URI", "Give <a href="http://myopenlink.net/dataspace/person/kidehen#this" id="link-id140eab68">me</a> a de-referencable URI" etc..</cite> </blockquote> <p>And each time, you respond with a <a href="http://dbpedia.org/resource/Uniform_Resource_Locator" id="link-id112c1860">URL</a> -- which to the best of your <a href="http://dbpedia.org/resource/World_Wide_Web">Web</a> <a href="http://dbpedia.org/resource/Knowledge" id="link-id140b51c0">knowledge</a> is a bona fide URI. But to your utter confusion you are told: Nah! You gave me a Document URI instead of the URI of a real-world thing or object etc..</p> <h3>What's up with that?</h3> <p>Well our everyday use of the Web is an unfortunate conflation of two distinct things, which have Identity: Real World Objects (RWOs) & Address/Location of Documents (<a href="http://dbpedia.org/resource/Information" id="link-id144838b0">Information</a> bearing Resources).</p> <p>The "Linked Data" meme is about enhancing the Web by unobtrusively reintroducing its core essence: the generic HTTP URI, a vital piece of Web Architecture DNA. Basically, its about so realizing the full capabilities of the Web as a platform for Open Data Identification, Definition, Access, Storage, Representation, Presentation, and Integration.</p> <h3>What is a Real World Object?</h3> <p>People, Places, Music, Books, Cars, Ideas, Emotions etc..</p> <h3>What is a URI?</h3> <p>A Uniform Resource Identifier. A global identifier mechanism for network addressable data items. Its sole function is Name oriented Identification.</p> <h4>URI Generic Syntax</h4> <p>The constituent parts of a URI (from <a href="http://www.ietf.org/rfc/rfc2396.txt" id="link-id1180c700">URI Generic Syntax RFC</a>) are depicted below: <img src="http://virtuoso.openlinksw.com/images/generic_uri_syntax_image.png" /> </p> <h3>What is a URL?</h3> <p>A location oriented HTTP scheme based URI. The HTTP scheme introduces a powerful and inherent duality that delivers:</p> <ol> <li> Resource Address/Location Identifier</li> <li> Data Access mechanism for an Information bearing Resource (Document, File etc..) </li> </ol> <p>So far so good!</p> <h3>What is an HTTP based URI?</h3> <p>The kind of URI <a href="http://dbpedia.org/resource/Linked_Data" id="link-id11100a28">Linked Data</a> aficionados mean when they use the term: URI.</p> <p>An HTTP URI is an HTTP scheme based URI. Unlike a URL, this kind of HTTP scheme URI is devoid of any Web Location orientation or specificity. Thus, Its inherent duality provides a more powerful level of abstraction. Hence, you can use this form of URI to assign Names/Identifiers to Real World Objects (RWO). Even better, courtesy of the Identity/Address duality of the HTTP scheme, a single URI can deliver the following:</p> <ol> <li> RWO Identfier/Name</li> <li> RWO Metadata document Locator (courtesy of URL aspect) </li> <li> Negotiable Representation of the Located Document (courtesy of HTTP's content negotiation feature).</li> </ol> <h3>What is Metadata?</h3> <p> Data about Data. Put differently, data that describes other data in a structured manner.</p> <h3>How Do we Model Metadata?</h3> <p>The predominant model for metadata is the <a href="http://dbpedia.org/resource/Entity-attribute-value_model" id="link-id11193d30">Entity</a>-Attribute-Value + Classes & Relationships model (<a href="http://dbpedia.org/resource/Entity-attribute-value_model" id="link-id11725710">EAV</a>/CR). A model that's been with us since the inception of modern computing (long before the Web). </p> <h3>What about RDF?</h3> <p>The Resource Description Framework (RDF) is a framework for describing Web addressable resources. In a nutshell, its a framework for adding Metadata bearing Information Resources to the current Web. Its comprised of:</p> <ol> <li> Entity-Attribute-Value (aka. Subject-Predictate-Object) plus Classes & Relationships (<a href="http://dbpedia.org/resource/Data_dictionary" id="link-id138df0f8">Data Dictionaries</a> e.g., <a href="http://dbpedia.org/resource/Web_Ontology_Language" id="link-id116bf590">OWL</a>) metadata model</li> <li> A plethora of instance data representation formats that include: <a href="http://dbpedia.org/resource/RDFa" id="link-id13360b90">RDFa</a> (when doing so within (X)HTML docs), Turtle, N3, TriX, RDF/XML etc. </li> </ol> <h3>What's the Problem Today?</h3> <p>The ubiquitous use of the Web is primarily focused on a Linked Mesh of Information bearing Documents. URLs rather than generic HTTP URIs are the prime mechanism for Web tapestry; basically, we use URLs to conduct Information -- which is inherently subjective -- instead of using HTTP URIs to conduct "Raw Data" -- which is inherently objective. </p> <blockquote> <strong>Note:</strong> Information is "data in <a href="http://dbpedia.org/resource/Context_%28language_use%29" id="link-id1395ca50">context</a>", it isn't the same thing as "Raw Data". Thus, if we can link to Information via the Web, why shouldn't we be able to do the same for "Raw Data"?</blockquote> <h3>How Does the Link Data <a href="http://dbpedia.org/resource/Meme" id="link-id1160ab70">meme</a> solve the problem?</h3> <p>The meme simply provides a set of guidelines (best practices) for producing Web architecture friendly metadata. Meaning: when producing EAV/CR model based metadata, endow Subjects, their Attributes, and Attribute Values (optionally) with HTTP URIs. By doing so, a new level of Link Abstraction on the Web is possible i.e., "Data Item to Data Item" level links (aka <a href="http://dbpedia.org/resource/Linked_Data" id="link-id137a78a0">hyperdata</a> links). Even better, when you de-reference a RWO hyperdata link you end up with a negotiated representations of its metadata.</p> <h3>Conclusion</h3> <p>Linked Data is ultimately about an HTTP URI for each item in the <a href="http://dbpedia.org/resource/Data_hierarchy" id="link-id1393c3e0">Data Organization Hierarchy</a> :-)</p> <h3>Related</h3> <ol> <li> <a href="http://www.nabble.com/Review-of-new-HTTPbis-text-for-303-See-Other-to24035004.html#a24774368" id="link-id10fcaba8">History of how "Resource" became part of URI</a> - historic account by <a href="http://www.w3.org/People/Berners-Lee/card#i" id="link-id1172b128">TimBL</a> </li> <li> <a href="http://www.w3.org/DesignIssues/LinkedData.html" id="link-id1338cbd0">Linked Data Design Issues Document</a> - <a href="http://www.w3.org/People/Berners-Lee/card#i" id="link-id13536ad8">TimBL</a>'s initial Linked Data Guide</li> <li> <a href="http://www.openlinksw.com/dataspace/kidehen@openlinksw.com/weblog/kidehen@openlinksw.com%27s%20BLOG%20%5B127%5D/1561" id="link-id116c1af8">Linked Data Rules Simplified</a> - My attempt at simplifying the Linked Data Meme without <a href="http://dbpedia.org/resource/SPARQL" id="link-id116c3b40">SPARQL</a> & RDF distraction</li> <li> <a href="http://www.openlinksw.com/dataspace/kidehen@openlinksw.com/weblog/kidehen@openlinksw.com%27s%20BLOG%20%5B127%5D/1547" id="link-id135dd1b8">Linked Data & Identity</a> - another related post</li> <li> <a href="http://www.openlinksw.com/dataspace/kidehen@openlinksw.com/weblog/kidehen@openlinksw.com%27s%20BLOG%20%5B127%5D/1565" id="link-id134afc50">The Linked Data Meme's Value Proposition</a> </li> <li> <a href="http://delicious.com/kidehen/identifier_scheme" id="link-id14cc7e18">My Del.icio.us hosted Bookmark Data Space for Identity Schemes</a> </li> <li> <a href="http://www.ted.com/talks/tim_berners_lee_on_the_next_web.html" id="link-id115a3748">TimBL's Ted Talk re. "Raw Linked Data"</a>.</li> </ol>
The URI, URL, and Linked Data Meme's Generic HTTP URI (Updated)
2009-10-07T12:02:34Z
2009-10-07T08:02:34-04:00
Kingsley Uyi Idehen
kidehen@openlinksw.com