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Re: QName URI mapping

From: Graham Klyne <GK@ninebynine.org>
Date: Wed, 23 Jan 2002 10:19:51 +0000
Message-Id: <5.1.0.14.2.20020123100044.00accbc0@joy.songbird.com>
To: "Jonathan Borden" <jborden@mediaone.net>
Cc: <www-rdf-comments@w3.org>
Jonathan,

You make fair comments, I think.

I think this (particularly your 3rd paragraph below) touches on a related 
issue [1], which I believe clearly is architectural, namely the use of a 
URI+fragment in RDF as a "first class resource identifier" not being 
entirely consistent with its use in the wider web.

I think this is an issue that probably needs to be resolved in a forum with 
broader scope than RDFcore (such as TAG?), because at heart it relates to 
compatibility between different systems.  For itself, not taking account of 
alternative XML usage, I still think that RDF is reasonably self-consistent.

#g

[1] http://www.w3.org/2000/03/rdf-tracking/#rdfms-fragments
     (and in particular, my point 1 in:
     http://lists.w3.org/Archives/Public/www-rdf-interest/2000Sep/0032.html )


At 12:37 AM 1/23/02 -0500, Jonathan Borden wrote:
>Graham Klyne wrote:
>
>"
>The forward transformation from QName -> URI is clear and unambiguous per
>the original RDF specification.  It is the reverse transformation that is
>problematic.
>"
>
>To be clear, while I would prefer that a bidirectional mapping be possible,
>just as I would _greatly_ prefer that the RDF model <-> XML mapping be
>bidirectional and roundtripable, there are issues with the simple forward
>transformation.
>
>In particular the model XML Schema uses for use of a QName as a type
>specifier is that the namespace name/URI is like the 'base URI' of the
>schema (quotes because it is not quite that simple but nonetheless) and that
>the localname is used as a locator for the type declaration within the
>schema module. In URI terms, XML Schema thus treats the localname LIKE a
>fragment identifier. It is not exactly a fragment identifier for several
>reasons, namely that no fragment identifer syntax is (yet)defined for
>application/xml and particularly because the localname maps to the XML
>Schema "name" attribute which is not ot type ID.
>
>For this reason I have issues with the forward QName -> URI mapping if this
>is a simple string concatenation.
>
>For the vast majority of RDF namespaces, perhaps all of the deployed RDF
>namespaces, simple concatenation is exactly the same as treating the
>localname as a fragment identifier (it comes after the '#') but for XML
>namespaces in general this is not the case. RDF does not require its
>namespaces to end in '#' hence one of the reasons for the incompatibility.
>
>I cannot say for sure that this incompatibility is entirely the 'fault' of
>RDF (although the mapping is perhaps too simplistic), rather a breakdown in
>communications and coordination between the RDF WG and other WGs more
>intimately involved in XML activities. It is not important to me where this
>incompatibility gets fixed, and since it is a basic architectural issue I
>agree with Brian and Tim Bray that the TAG ought be involved in this issue.
>For that reason alone, I would prefer that the issue not be closed for the
>moment.
>
>Jonathan

------------
Graham Klyne
GK@NineByNine.org
Received on Wednesday, 23 January 2002 06:24:21 GMT

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