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Re: xml literal and xslt (resend)

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Mon, 11 Mar 2002 12:24:31 +0000
Message-Id: <5.1.0.14.2.20020311120137.00a01c80@joy.songbird.com>
To: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
Cc: <w3c-rdfcore-wg@w3.org>
At 11:27 AM 3/11/02 +0000, Jeremy Carroll wrote:
>2: Use of Exclusive Canonicalization
>====================================
>
>There is only one XML spec that I am aware of which worries in this sort of
>way about referring to namespaces; ignoring ones that are not used. That
>spec is the exclusive canonicalization spec. The key concept is:
>http://www.w3.org/TR/2002/CR-xml-exc-c14n-20020212#def-visibly-utilizes
>
>[[[
>An element E in a document subset visibly utilizes a namespace declaration,
>i.e. a namespace prefix P and bound value V, if E or an attribute node in
>the document subset with parent E has a qualified name in which P is the
>namespace prefix. A similar definition applies for an element E in a
>document subset that visibly utilizes the default namespace declaration,
>which occurs if E has no namespace prefix
>]]]
>
>(that is the only new concept in exc-c14n).
>
>
>Using this concept we could imagine a statement like:
>
>"An xml literal includes the namespaces which are visibly utilized by that
>literal, and no others."
>
>or (more strongly)
>
>"An xml literal is formed by taking the exclusive canonicalization of the
>element content."

My natural inclination is to think that namespaces explicitly defined in 
the literal should be preserved...

What about a_4.xml?:

[[[
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:eg="http://example.org/" >
    <rdf:Description>
      <eg:a rdf:parseType="Literal">
          <foo xmlns:eg="http://example.org/" />
      </eg:a>
    </rdf:Description>
</rdf:RDF>
]]]

or this:

[[[
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:eg="http://example.org/" >
    <rdf:Description>
      <eg:a rdf:parseType="Literal">
          <foo xmlns:eg="http://example.org/" 
xmlns:eg1="http://example1.org/" />
      </eg:a>
    </rdf:Description>
</rdf:RDF>
]]]

or even this:

[[[
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:eg="http://example.org/" >
    <rdf:Description>
      <eg:a rdf:parseType="Literal">
          <foo xmlns:eg="http://example.org/"
               xmlns:eg1="http://example1.org/" attr='eg1:qname' />
      </eg:a>
    </rdf:Description>
</rdf:RDF>
]]]

Does the declaration of a namespace within the XML fragment constitute a 
"visible utilization" of the namespace?

...

I see you've addressed this in the following sections, and conclude that 
the answer is "No":  an explicit namespace declaration does not constitute 
a visible utilization.  Which, as you point out, creates a problem.

I'm bothered with all the solutions you propose -- XML schema uses qnames 
in attributes, so I think we'd ignore this at some risk.  The solution of 
using rdf:parseType="literal ns1 ns2 ..." doesn't seem to be XSLT-safe.

I find myself foundering on exactly what it means to be XSLT-safe:  it 
seems that any XSLT solution that naively extracts literal content is 
likely to fall foul if this goal.

#g



------------------------------------------------------------
Graham Klyne                    MIMEsweeper Group
Strategic Research              <http://www.mimesweeper.com>
<Graham.Klyne@MIMEsweeper.com>
Received on Monday, 11 March 2002 07:24:15 EST

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