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LC-199: A schema for the schemaless

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 07 Oct 2000 12:18:09 +0100
To: Paul Cotton <pcotton@microsoft.com>
Cc: www-xml-schema-comments@w3.org
Message-ID: <f5bd7hc99xq.fsf@cogsci.ed.ac.uk>
The W3C XML Schema Working Group has spent the last several months
working through the comments received from the public on the last-call
draft of the XML Schema specification.  We thank you for the comments
you made on our specification during our last-call comment period, and
want to make sure you know that all comments received during the
last-call comment period have been recorded in our last-call issues
list (http://www.w3.org/2000/05/12-xmlschema-lcissues).

Among other issues, you raised the point registered as issue LC-199,
requesting that schema-validity assessment always produce usable
output for Query processing, even in the absence of a schema.

The WG has agreed with this request, having established a task force
which discussed the issue at some length both internally, with the
Query WG, and at an XML Schema f2f.  The resolution is embodied in a
number of aspects of the recently published working draft [1],
summarised as follows:

 1) Schema-validity assessment is possible in the absence of a schema, 
or in the presence of a schema with little or no relevant information
about the instance being assessed;

 2) Schema-validity assessment outcomes include information not only
about validity as such, but about the degree of validation attempted;

 3) Lax validity assessment, i.e. assessment wrt the unconstrained
type (a.k.a the ur-type, whose name is variously 'anyType' or
'anySimpleType'), is the fallback in all cases where no explicit type
definition is available, and this validation is recorded in the PSVI
as usual.

It follows from this that schema-validity assessment can be required
unconditionally as a pre-condition for Query processing, and that it
will always result in minimal type definition information throughout
the PSVI (subject to appropriate processor parameterisation, which
Query can require _be_ appropriate).

It would be helpful to us to know whether you are satisfied with the
decision taken by the WG on this issue, or wish your dissent from the
WG's decision to be recorded for consideration by the Director of
the W3C.

  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 Saturday, 7 October 2000 07:18:12 UTC

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