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Re: Question about VR Element Locally Valid (Element) in Structures 3.3.4

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 06 Apr 2003 13:21:34 +0100
To: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
Cc: W3C XML Schema Comments list <www-xml-schema-comments@w3.org>
Message-ID: <f5bk7e7sto1.fsf@erasmus.inf.ed.ac.uk>

"C. M. Sperberg-McQueen" <cmsmcq@acm.org> writes:

> 1 is there not a term we can use for xsi:type-specified types which is
> less subject to misunderstanding than 'local type definition'?  The
> types denoted here by this phrase are not local to a given element
> declaration, and it just seems like offering a pawn to fate to use the
> word 'local' here.  Call them 'dynamic', call them
> 'instance-specified', call them 'types with polka dots', but is it
> really essential to call them 'local'?

No problem -- this is a locally-defined term, which can easily be change. 

> 2 Clause 5.1.1 seems to suggest that it's only an error for an element
> instance to require / use a default value if the element instance has
> an xsi:type attribute.  I think this is probably because the other
> case is catered for somewhere else, but I think it's a needless
> complication.  I think clause 5.1.1 can and should be simplified to
> say:
>    5.1.1 The canonical lexical representation of the {value constraint}
>    value must be a valid default for the actual type definition as
>    defined in Element Default Valid (Immediate) (3.3.6).
> I think this is easier to understand both syntactically and from a
> design point of view.  Is there any reason not to change it?

Yes, in my opinion.  What does in fact already exist is a Schema
Component Constraint (Element Declaration Properties Correct).  This
means that schemas with element declarations whose default isn't
type-valid per their declared types aren't schemas at all.  Making the
change you suggest above would appear to turn this into a runtime
error.  I think that would be a retrograde step.

  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@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Sunday, 6 April 2003 08:21:41 UTC

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