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Re: Non-deterministic content model

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 17 Jan 2001 09:35:37 +0000
To: Michael Anderson <michael@research.canon.com.au>
Cc: "Joseph M. Reagle Jr." <reagle@w3.org>, xmlschema-dev@w3.org, Noah_Mendelsohn@lotus.com
Message-ID: <f5b3deio712.fsf@cogsci.ed.ac.uk>
Michael Anderson <michael@research.canon.com.au> writes:

> > <snip/>
> > Also, I guess it's true to say a schema can
> > have errors that will not be addressed upon validation, but only upon
> > validation of its instances?
> 
> I don't believe it is true for your example.  If the content model
> of a schema is non-deterministic I believe this is an error,
> regardless of whether your instance includes the offending ambiguous
> information item, or not (as in your instance).

Correct.  As it happens, XSV is not conformant in this area, in that
it doesn't build an FSM for a content model until it needs it, and it
doesn't detect the violation until then.

> Your statement can be true (IMO) with respect to other constraints,
> such as missing schema sub-components.  So let us say that your
> above shema did not have the <any>.  Now let us remove the
> <simpleType name="HMACOutputLengthType"> and assume that the
> processor has no way of finding this simpleType through other means.
> Now, no errors will be found with this schema when you validate your
> particular instance because you do not have an HMACOutputLength
> information item.  If you _did_have_ an HMACOutputLength information
> item in your _instance_ then there would have been an error in your
> _schema_ as it could not resolve the HMACOutputLengthType definition
> that it was required to.

This is a correct analysis.

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, 17 January 2001 04:35:40 GMT

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