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Re: Status of Link header

From: Shane McCarron <shane@aptest.com>
Date: Fri, 12 Sep 2008 09:29:23 -0500
Message-ID: <48CA7CC3.5000106@aptest.com>
To: Julian Reschke <julian.reschke@gmx.de>
CC: HTTP Working Group <ietf-http-wg@w3.org>

Sorry - let me be more precise.  It appears to me that the current draft 
is deferring to the simple relation descriptions from HTML 4.  Those 
definitions are very, very old and there has been work done recently on 
this with the W3C.  These have been recently updated and extended as 
part of the XHTML 2 Working Group / RDFa Task Force activity defining 
RDFa.  That activity defines a mechanism for extending the collection of 
relationships via RDF, and also codifies the pre-defined "simple" 
relationships such as previous.  I was only saying that if you want this 
document to be consistent with the direction HTML is headed, you should 
rely upon the definitions in RDFa.  Those definitions are contained in 
the referenced vocabulary document.

As to registration - I don't personally expect there to be extensions to 
the collection of simple relationships.  If there are, it would be done 
through the W3C processes and the vocabulary document updated.

Instead, I expect RDF vocabularies to be created that extend the 
collection.  Since the draft Link: header document defines a 
relationship as a "URI-Reference" I think this is entirely consistent 
with the definition used for values of @rel in RDFa.  After all, RDF is 
about expressing semantics via URIs. 

For more on RDFa, you might look at http://www.w3.org/TR/rdfa-syntax

As an aside, RDFa syntactically uses "CURIEs" to express values for 
@rel.  This is a lexical space concept, not a value space concept.  In 
the value space, @rel values are URIs, so I believe this to be entirely 
consistent with the view that Link: header rel parameters are 
white-space separated URI-References. 

Julian Reschke wrote:
> Shane McCarron wrote:
>> Mark,
>> I think that you should defer to the spec at 
>> http://www.w3.org/1999/xhtml/vocab for the definitive list of rel and 
>> rev values.  That document is written in XHTML+RDFa and is maintained 
>> as part of the W3C process for defining XHTML.
>> ...
> a) What's the registration process?
> b) Why would it be a good idea to have relations between resources 
> being defined specifically for one vocabulary? Shouldn't relation 
> names be re-usable between HTML, XHTML, Atom, and other formats (*)?
> BR, Julian
> (*) for instance those that are not XML based and need the Link header 
> to transport it

Shane P. McCarron                          Phone: +1 763 786-8160 x120
Managing Director                            Fax: +1 763 786-8180
ApTest Minnesota                            Inet: shane@aptest.com
Received on Friday, 12 September 2008 14:30:02 UTC

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