This link has been bookmarked by 30 people . It was first bookmarked on 19 Jun 2012, by Lisa Spiro.
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18 Jan 16
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22 Sep 15
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Given only a URI, machines and people should be able to retrieve a description about the resource identified by the URI from the Web. Such a look-up mechanism is important to establish shared understanding of what a URI identifies. Machines should get RDF data and humans should get a readable representation, such as HTML. The standard Web transfer protocol, HTTP, should be used.
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There should be no confusion between identifiers for Web documents and identifiers for other resources. URIs are meant to identify only one of them, so one URI can't stand for both a Web document and a real-world object.
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22 Apr 15
Byron CochraneFrom OWS 11 LD discussion 4-22-15
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31 Oct 14
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17 Jul 14
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24 Feb 14
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10 Dec 13
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all information has to be expressed as statements about resources, like the members of the company Example.com are Alice and Bob or Bob's telephone number is "+1 555 262" or this Web page was created by Alice
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Web documents have always been addressed with URIs (in common parlance often referred as Uniform Resource Locators, URLs). This is useful because it means we can easily make RDF statements about Web pages, but also dangerous because we can easily mix up Web pages and the things, or resources, described on the page.
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term Information Resource is used instead of Web document.
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RDF/XML, the standard serialisation format of RDF, has its own content type, application/rdf+xml
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real-world objects or things
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Given only a URI, machines and people should be able to retrieve a description about the resource identified by the URI from the Web. Such a look-up mechanism is important to establish shared understanding of what a URI identifies. Machines should get RDF data and humans should get a readable representation, such as HTML. The standard Web transfer protocol, HTTP, should be used.
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What URI should we use instead of the placeholder <URI-of-alice>? Certainly not http://www.example.com/people/alice, because that would confuse a person with a Web document, leading to misunderstandings: Is the homepage of Alice also named “Alice”? Can a homepage itself have an e-mail address? And does it make sense for a home-page to have itself as its home-page? So we need another URI. (For in-depth treatments of this issue, see What HTTP URIs Identify? [HTTP-URI2] and Four Uses of a URL: Name, Concept, Web Location and Document Instance [Booth]).
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here should be no confusion between identifiers for Web documents and identifiers for other resources. URIs are meant to identify only one of them, so one URI can't stand for both a Web document and a real-world object.
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he first solution is to use “hash URIs” for non-document resources. URIs can contain a fragment, a special part that is separated from the rest of the URI by a hash symbol (“#”).
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second solution is to use a special HTTP status code, 303 See Other, to give an indication that the requested resource is not a regular Web document.
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Which approach is better? It depends. The hash URIs have the advantage of reducing the number of necessary HTTP round-trips, which in turn reduces access latency. A family of URIs can share the same non-hash part. The descriptions of http://www.example.com/about#exampleinc, http://www.example.com/about#alice, and http://www.example.com/about#bob are retrieved with a single request to http://www.example.com/about. However this approach has a downside. A client interested only in #product123 will inadvertently load the data for all other resources as well, because they are in the same file. 303 URIs, on the other hand, are very flexible because the redirection target can be configured separately for each resource. There could be one describing document for each resource, or one large document for all of them, or any combination in between. It is also possible to change the policy later on.
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Note also, that both 303 and Hash can be combined, allowing a large dataset to be separated into multiple parts and have an identifier for a non-document resource. An example for a combination of 303 and Hash is:
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URIs of the bob#this form can be used for large sets of data that are, or may grow, beyond the point where it is practical to serve all related resources in a single document.
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07 Aug 13
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12 May 13
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24 Nov 12
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On the Semantic Web, URIs identify not just Web documents, but also real-world objects like people and cars, and even abstract ideas and non-existing things like a mythical unicorn. We call these real-world objects or things.
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- 1. Be on the Web.
- Given only a URI, machines and people should be able to retrieve a description about the resource identified by the URI from the Web. Such a look-up mechanism is important to establish shared understanding of what a URI identifies. Machines should get RDF data and humans should get a readable representation, such as HTML. The standard Web transfer protocol, HTTP, should be used.
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- 2. Be unambiguous.
- There should be no confusion between identifiers for Web documents and identifiers for other resources. URIs are meant to identify only one of them, so one URI can't stand for both a Web document and a real-world object.
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14 Nov 12
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Content-Location
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search engines can refer to the different representations by using the different URIs
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302 Found
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this approach allows Web authors to link directly to a specific representation.
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Content negotiation thus allows publishers to serve HTML representations of a Web document to traditional Web browsers and RDF representations to Semantic Web-enabled user agents
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application/rdf+xml
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hash URIs.
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303 URIs
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clients can bookmark
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using the original URI, e.g. http://www.example.com/id/alice
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reducing the number of necessary HTTP round-trips
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hash URI
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downside
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303 URIs
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We advise to additionally provide SPARQL endpoints or comparable services to answer complex queries on the server directly, rather than to let the client download a large set of data via HTTP.
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this in the above URI is a suggestion you may want to copy for your implementations.
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One good practice is to include the current year in the URI path
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all 303 URIs
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should also be explicitly linked with each other
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All the URIs related to a single real-world object
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foaf:page <http://www.example.com/people/alice>; rdfs:isDefinedBy <http://www.example.com/data/alice>;
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The HTML document at http://www.example.com/people/alice should contain in its header a <link> element that points to the corresponding RDF document:
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link rel="alternate" type="application/rdf+xml" title="RDF Representation" href="http://www.example.com/data/alice" />
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If the RDF data is about
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rel="meta"
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The RDF document for Chris Bizer is a SPARQL query result from the server's SPARQL endpoint:
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6.1. New URI Schemes
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19 Jun 12
Lisa Spiro"The Resource Description Framework RDF allows users to describe both Web documents and concepts from the real world—people, organisations, topics, things—in a computer-processable way. Publishing such descriptions on the Web creates the Semantic Web. URIs (Uniform Resource Identifiers) are very important, providing both the core of the framework itself and the link between RDF and the Web. This document presents guidelines for their effective use. It discusses two strategies, called 303 URIs and hash URIs. It gives pointers to several Web sites that use these solutions, and briefly discusses why several other proposals have problems. "
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07 Oct 11
emresevincThe Resource Description Framework RDF allows users to describe both Web documents and concepts from the real world—people, organisations, topics, things—in a computer-processable way. Publishing such descriptions on the Web creates the Semantic Web. URIs
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