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Fragments in RDF and HTML

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Tue, 27 Sep 2005 13:56:10 +0100
Message-ID: <4339416A.6080701@hplb.hpl.hp.com>
To: public-rdf-in-xhtml-tf <public-rdf-in-xhtml-tf@w3.org>



In response to my outstanding action.

I have reviewed

http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-fragID


Top-level summary: no problem, but a lot of dancing on pin-heads.

(it's only three or four paras)

Key statements:

First para - problem statement.

[[
RDF uses an RDF URI Reference, which may include a fragment identifier, 
as a context free identifier for a resource. RFC 2396 [URI] states that 
the meaning of a fragment identifier depends on the MIME content-type of 
a document, i.e. is context dependent.
]]

i.e. we would normally expect ...doc.html#frag to have a meaning 
depending on an HTML mime type, which is an anchor within a document, or 
some subsection of the document or something ...., but RDF doesn't take 
this point of view.

Second para - resolution.

[[
a URI reference in an RDF graph is treated with respect to the MIME type 
application/rdf+xml
]]

i.e. wherever the fragment identifier originally came from, the RDF view 
forces a particular mime type.

Also
[[
Note that nothing here requires that an RDF application be able to 
retrieve any representation of resources identified by the URIs in an 
RDF graph.
]]

So, in summary, RDF Concepts has the weasels words already prepared.

In these terms, an XHTML2 document and frag ID doc.xhtml2#frag when used 
within RDF/A is implicitly understood as if there was an RDF/XML 
representation retrievable with the mime type application/rdf+xml.
i.e. it is as if everyone who publishes an XHTML2 document has set their 
server up with the GRDDL transform and the appropriate mime type magic 
so that an RDF/XML representation of the fragment is retrievable; and it 
is that representation fragment rather than the HTML one that is being 
discussed. Not quite clear how you talk about the HTML document 
subsection as a piece of HTML rather than as an abstract resource, 
perhaps you can't really, or at least need an extended vocabulary to do 
so. The normal usage is that the doc.xhtml2#frag identifies a secondary 
resource which may be described (incompletely) in RDF, and have a 
representation in HTML, but is not, in itself, either its RDF 
description or its HTML representation.

What fun ...

Jeremy
Received on Tuesday, 27 September 2005 12:59:24 GMT

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