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Re: Summary of the QName to URI Mapping Problem

From: Dan Connolly <connolly@w3.org>
Date: Thu, 16 Aug 2001 07:46:34 -0500
Message-ID: <3B7BC0AA.F0314055@w3.org>
To: Piotr Kaminski <pkaminsk@home.com>
CC: www-rdf-logic@w3.org
Piotr Kaminski wrote:
> 
> Dan Connolly said:
> > The RDF spec includes an unambiguous QName -> URI mapping:
> > uri(qname) = concat(nsname(qname), localname(qname))
> 
> The mapping mechanism is indeed unambiguously defined.  It can, however,
> lead to invalid results.
> 
> Let's start from the following axioms.
> 1.  A QName identifies a (single) resource.

I don't take that as an axiom. I don't see why one would.

I am aware of specs that are inconsistent
with this notion; for example, XML Schemas
map the same qname to different element types depending
on context.

> 2.  A URI identifies a (single) resource.
> 3.  The goal of a QName -> URI mapping is to transform a QName into a URI
> that identifies the *same* resource.
> 
> The above mapping doesn't achieve the goal.  An example follows that is
> essentially equivalent to Patrick's, but I have a feeling that most of the
> contention will be about the axioms above, especially (1).  One could take
> the position that a QName is a purely syntactic construct, and doesn't
> identify anything in and of itself.

Yes.

>  I believe such an interpretation
> contradicts the XML Namespaces recommendation, in spirit if not in letter.

I disagree. I believe you're reading more into the namespaces spec
than is there.

The namespaces spec allows folks to associate URI references with
some attributes and elements. That's all. It doesn't even
define the term "namespace" in any testable/observable way.


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 16 August 2001 08:46:38 GMT

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