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Re: [Bulk] Trying to Understand Complex Abstract Types: How ToDefine?

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Thu, 24 Mar 2005 16:45:39 +0000
To: Eliot Kimber <ekimber@innodata-isogen.com>
Cc: xml-schema-dev <xmlschema-dev@w3.org>
Message-ID: <f5bzmwtngb0.fsf@erasmus.inf.ed.ac.uk>

Eliot Kimber <ekimber@innodata-isogen.com> writes:

> - If the supertype content model allows A+ then any combination of
> elements derived from A, in any order, is allowed in specialized
> content models. In XSD if the supertype content model is A+ then all
> you can do in a restriction substitution group is have *exactly one*
> particle whose type is A. This is a serious restriction.

This will be fixed in Schema 1.1.

> - If the supertype content model allows (A | B) then specializations
> may allow elements specialized from just A, just B, or A and B, in
> either order. XSD requires that the order of particles be preserved,
> even when the base content model allows either order.

A _and_ B, he says with some surprise?  ( A | B ) only allows one item
in the input.  A & B allows two.  That's a rather odd change from a
semantic point of view. . .

I'd be interested in seeing an example which motivates that a bit
more. . .

If you meant (A | B)*, then again, you have a reasonable gripe, and
this will be fixed in Schema 1.1.

> <snip/>

> There's always the next revision of the spec....

See above :-)

 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Thursday, 24 March 2005 16:45:44 UTC

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