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I read the thread. The only person who points a genuine issue with Chameleon schemas is Jeni Tennison. The issue she points out is related to everyone's favorite mis-feature, QNames-in-content. Henry T mentions that it should be fixed but I don't see how that will be done cleanly without adding more complexity and/or confusion.
Instead of another special-case work around, I'd rather the REC said DON'T DO THIS, IT IS DUMB instead of adding complexity by somehow "fixing" it. Of course, an elegant solution may exist which I've overlooked.
-----Original Message-----
From: Murali Mani [mailto:mani@CS.UCLA.EDU]
Sent: Mon 9/2/2002 6:27 PM
To: Michael Leditschke
Cc: Dare Obasanjo; xml-dev@lists.xml.org
Subject: RE: [xml-dev] xml schema
I was just following the kind of discussion which followed that mail in
xmlschema-dev between Kawaguchi-san, Henry Thompson and others.. I think
it is interesting to note:
http://lists.w3.org/Archives/Public/xmlschema-dev/2001Oct/0130.html
http://lists.w3.org/Archives/Public/xmlschema-dev/2001Oct/0128.html
http://lists.w3.org/Archives/Public/xmlschema-dev/2001Oct/0127.html
I guess you get a range of opinions on the chameleon schemas here..
further more, you can get why try to include such a difficult thing in
this note
http://lists.w3.org/Archives/Public/xmlschema-dev/2001Oct/0129.html
hope this helps.. cheers and regards - murali.
On Tue, 3 Sep 2002, Michael Leditschke wrote:
> Dare wrote:
>
> > The advice on avoiding chameleon schemas could be fleshed out.
>
> I don't wish to enter the debate about the man vs the matter, but
> on matters of fact, the example given of chameleon schemas is
> factually incorrect, I believe.
>
> Error 1: Reference to person type in main schema.
>
> The master schema makes reference to
>
> <xs:element ref="person" maxOccurs="unbounded" />
>
> refs are treated as QNames, and without a default namespace,
> "person" is a reference to {None}person.
>
> Having no namespace, the definition of person in the included
> schema is coerced into the http://example.com namespace. Thus
> the validator should complain about the reference to person
> in the including schema and XSV and MSXML do.
>
>
> Error 2: Assertion that ref="familyName" should explictly placed in
> the http://example.com namespace.
>
> Any ref with a {None} namespace in a chameleon schema will be coerced
> into the namespace of the includer. Thus there is NO need to explicitly
> place familyName in the target namespace. Indeed, if this assertion
> were correct, chameleon schemas would be pretty useless. See
>
> http://lists.w3.org/Archives/Public/xmlschema-dev/2001Oct/0123.html
>
> With error one above corrected, both XSV and MSXML validate the included
> schema without change to the included schema.
>
>
> The author's other points may or may not be valid, and the use of chameleon
> schemas may or may not be bad, but factual errors tend to cloud the issue
> and lead to suspicion about the validity of the other arguments put forward
> by the author(as distinct from suspicions about the author themselves).
>
> Regards
> Michael
>
>
>
>
>
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