- From: Tim Berners-Lee <timbl@w3.org>
- Date: Tue, 17 Sep 2002 22:51:18 -0400
- To: "Williams, Stuart" <skw@hplb.hpl.hp.com>
- Cc: www-tag@w3.org
- Message-Id: <814A1EC6-CAB1-11D6-A525-000393914268@w3.org>
Indeed, Section 4.2 was what I was thinking of, < http://www.w3.org/TR/rdf-concepts/#xtocid103660 > . Tim _________ """4.2 Fragment identifiers How should RDF treat a URI reference with a fragment identifier? Conventional web architecture has that the meaning of a fragment identifier is dependent on the MIME type of a resource that is obtained by dereferencing the URI part. URIs without fragment identifiers are generally presumed to map to some resource for which a Web representation (or several) can be retrieved. But RDF has no concept of a fragment identifier separate from a URI: RDF treats a URI reference as an opaque identifier that denotes some resource [RDF-SEMANTICS]. Further, an RDF resource identifier may denote something that is not web-retrievable; e.g. a car, or a Unicorn. These apparently conflicting interpretations can be reconciled if: * we assume that the URI part (i.e. excluding fragment identifier) of any URI reference used in an RDF document indicates a Web resource with an RDF representation. (If it is not dereferencable as such on the web, so be it, but we must assume its notional existence.) So when someurl#frag is used in an RDF document, someurl is presumed to designate an RDF document. * when used in an rdf document, someurl#frag means the thing that is indicated, according to the rules of the application/rdf+xml mime type as a "fragment" or "view" of the RDF document at someurl. If the document doesn't exist, or can't be retrieved, then exactly what that view may be is somewhat undetermined, but that doesn't stop us from using RDF to say things about it. * the RDF interpretation of a fragment identifier allows it to indicate a thing that is entirely external to the document, or even to the "shared information space" known as the Web. That is, it can be an abstract idea, like my car or a mythical Unicorn. * thus, an RDF document acts as an intermediary between some web retrievable documents (itself, at least, also any other web-retrievable URIs that it may use, including schema URIs and references to other RDF documents), and some set of abstract or non-Web entities that the RDF may describe. This provides a handling of URI referencess and their denotation that is consistent with the RDF model theory and usage, and also with conventional web axioms. This approach somewhat extends the idea of a "fragment" or "view" beyond the common idea (when handling web documents) that it is a physical part of a containing document. In view of this, it is reasonable to consider that URIs without fragment identifiers are most helpfully used for indicating web-retrievable resources (when used in RDF), and URIs with fragment identifiers are used for abstract ideas that don't have a direct web representation. This is not a hard-and-fast distinction, as the line between resources having or not having a web-retrievable representation is sometimes hard to draw precisely.""" On Monday, September 16, 2002, at 04:35 PM, Williams, Stuart wrote: > Tim, > > I think this is probably the RDF publication that you had in mind. > > http://www.w3.org/TR/rdf-concepts/ >
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