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Another way to go about it would be to have a special transformation to
"namespace-normalize" the instance document. This version would be used for
DTD Validation. The ns-normalized version could then be discarded, and the
actual instance document presented to the user or application for further
Nobody has done this though, because it would require:
1. changes to existing validating parsers
2. consensus on how to write DTDs that would work with this process (compare
DTDs for XML-Schema and XHTML for two different approaches).
This kind of change would be much easier if XML Processing were a nice
layered architecture. But it's not.
>From: "Rick Jelliffe" <email@example.com>
>To: "The Deviants" <firstname.lastname@example.org>
>Subject: Re: [xml-dev] life support for DTDs? was RE: [xml-dev]
>Date: Fri, 1 Feb 2002 21:52:14 +1100
> From: "Alan Kent" <email@example.com>
> > At the risk of looking like a fool (having started reading the thread
> > half way through), I don't quite understand the above. I would have
> > thought you would have done something like (syntax is indicative only)
> > <!XMLNS y "http://foo.bar/baz/">
> > <!XMLNS q "http://rumplestiltskin.com/">
> > <!ELEMENT y:x (y:a, q:a)>
> > <!ELEMENT y:a (#PCDATA)>
> > <!ELEMENT q:a (#PCDATA)>
> > <!ATTLIST q:a age CDATA #IMPLIED
> > q:type CDATA #FIXED "123">
> > The name spaces would be in scope for the DTD only (not instances).
> > It would allow you to mix different namespaces in one DTD. There would
> > be some scoping ssues to be resolved because you would want to import
> > other DTDs and not accidentally collide on namespace prefixes
> > (eg: DTD namespace declarations are local to the current external entity
> > or something like that).
>Oh, the thread was asking "could we extend DTDs to include namespaces?"
>and I was pointing out that we didn't need to change DTDs, just to
>widen their interpretation. That way we don't have to change any parsers
>or existing DTDs (except to add xmlns declarations for all elements)
>or existing documents, just the validators used. Of course,
>if you write a document that didn't use the literal names given in the DTD,
>that document would not validate if the DTD was used with XML 1.0, but
>that is no different from now.
>The approach of revising the DTD syntax for a special kind of schema
>has been tried before, but failed to thrive.
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