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[Bug 6202] All group extending "empty mixed" content

From: <bugzilla@wiggum.w3.org>
Date: Wed, 05 Nov 2008 11:58:22 +0000
To: www-xml-schema-comments@w3.org
Message-Id: <E1Kxh1i-0008Ug-94@farnsworth.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=6202





--- Comment #1 from Michael Kay <mike@saxonica.com>  2008-11-05 11:58:21 ---
It might also be worth observing that although the XML mapping rules never
generate a model group whose {compositor} is *all* and whose {particles} is
empty, the schema component model allows such a model group to exist. It
generally seems a bad idea to allow components to exist for which there is no
XML representation.

(HT has pointed out another case, the component model does not prevent an *all*
group containing particles other than element particles and wildcard
particles.)

On a related point, a singleton *sequence* and a singleton *all* model group
are equivalent from the point of view of validation, and from the point of view
of the rules on valid restriction; but they are not equivalent when it comes to
derivation by extension. (If operator syntax is used, as in (A,B) for sequence
or (A&B) for interleave, it becomes clear that for singleton groups there
should be no distinction.) Should we make them equivalent in the component
model, or at least allow both to be extended in the same ways?


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Received on Wednesday, 5 November 2008 11:58:31 GMT

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