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Re: Quick technical question.

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 21 Feb 2001 15:33:59 +0000
To: Michael Anderson <michael@research.canon.com.au>
Cc: "xmlschema-dev@w3.org" <xmlschema-dev@w3.org>
Message-ID: <f5bbsrwcaoo.fsf@cogsci.ed.ac.uk>
Michael Anderson <michael@research.canon.com.au> writes:

> "Henry S. Thompson" wrote:
> 
> > Michael Anderson <michael@research.canon.com.au> writes:
> >
> > > Hi all,
> > > Does someone understand clause 1.6 of
> > > http://www.w3.org/TR/xmlschema-1/#rcase-NameAndTypeOK ?
> > >
> > > "R's { type definition } is validly derived given {extension } from B's
> > > {type definition} as defined by Type Derivation OK (Complex)(5.11) or
> > > Type Derivation OK(Simple)(5.12) as appropriate".
> >
> > This means that the derivation can't involve {extension} -- it's as if
> > B had had block='extension'.  The point is that to derive by
> > restriction, the type derivation path can't involve extension.
> 
> Thanks for the reply.
> 
> Unfortunately i admit I'm still confused.  Having B's block='extension' just
> means that substitute groups of B can't have an extended type of B.

Sorry not to be clearer -- the {extension} is being used _here_ to
constrain the relation between the two types -- the actual constraint
used here doesn't know or care _why_ you're checking the two types, it 
just traces the connection and checks it exists and doesn't use the
prohibited derivation methods.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-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/
Received on Wednesday, 21 February 2001 10:34:02 UTC

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