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Re: [rdfmsQnameUriMapping-6] CLOSED: Algorithm for creating a URI from a QName?

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: Wed, 03 Dec 2003 15:48:41 +0000
To: Dan Connolly <connolly@w3.org>
Cc: "Williams, Stuart" <skw@hp.com>, "Ian B. Jacobs" <ij@w3.org>, Jonathan Borden <jborden@mediaone.net>, www-tag@w3.org
Message-ID: <f5bzne9x5pi.fsf@erasmus.inf.ed.ac.uk>

Dan Connolly <connolly@w3.org> writes:

> On Wed, 2003-12-03 at 08:24, Williams, Stuart wrote:
> [...]
>
>> Where I thought we landed was at the statement
>> Ian quoted [4] from our minutes:
>> 
>>   "The use of Qnames as identifiers without providing a mapping to 
>>    URIs is inconsistent with Web Architecture." 
>
> yes, quite.
>
>
>> I don't believe a mapping to URI is necessary when a qname is being used to
>> convey a qualified name! 
>
> On the contrary: where we landed follows from web architecture
> principle #1: The identification mechanism for the Web is the URI.

<snip/>

> Perhaps this is one of the exceptions, and whatever a:b
> refers to, we cannot "link to it, make or refute assertions about it,
> retrieve or cache a representation of it, include all or part of it by
> reference into another representation, annotate it, or perform other
> operations on it."
>  -- http://www.w3.org/2001/tag/2003/webarch-20031128/#identification

<snip/>

> and that where qnames are not used as identifying a Web Resource,
> that's outside of Web Architecture.

So this leads us to the following somewhat unhappy conclusion: XML 1.0
plus namespaces makes use of QNames in a way which is outside of Web
Architecture.

How do I conclude this?

Consider the following XML document

<?xml version="1.0"?>
<root xmlns:p="http://www.example.org/">
 <p:book>
  <p:title>The Mill on the Floss</p:title>
  <p:author>
   <p:person p:title="Ms" p:given="George" p:family="Eliot"/>
  </p:author>
 </p:book>
</root>

I claim this is a well-formed XML document, and it would be easy to
produce a DTD, W3C XML Schema, RNG schema, etc. to accurately
characterise it.

Now, just what Web Resource does the QName 'p:title' identify?  I
claim it is absolutely clear from the XML Namespaces REC that p:title
corresponds to the expanded name (== URI/local name pair) consisting
of the URI "http://www.example.org/" and the local name "title".

But given that this is evidently the name of both an element (type)
and an attribute (type) in the document given above (the document type
of the document given above), what could possibly be meant by "_the_
Web Resource identified" by the QName 'p:title'?

It seems clear to me there isn't one.  The Namespaces REC provides a
means for defining _names_.  It does _not_ place any requirements that
those names be univocal within a given context.  This seems perfectly
reasonable to me.  It follows, however, that the kind of names the
Namespaces REC defines cannot usefully be assumed to be in one-to-one
correspondence with Web Resources, even against the background context
supplied by a XML document type, however defined.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                      Half-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Wednesday, 3 December 2003 10:51:22 GMT

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