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fixed and default

From: Ian Stokes-Rees <ijs@decisionsoft.com>
Date: Fri, 20 Apr 2001 14:55:18 +0100
To: xmlschema-dev@w3.org
Message-Id: <E14qbNW-0002y6-00@tugela.dsl.net>
Section 2.2.1 of the XSDL Primer states:

Note that the concepts of a fixed value and a default value are mutually
exclusive, and so it is an error for a declaration to contain both
fixed and default attributes.

And yet the schema for schemas does nothing to assert the mutual exclusivity of
"fixed" and "default".  I just tried the Primer po.xsd schema on XSV with the
modification of adding a 'default="UK"' attribute and it reported that the
schema was fine, indicating to me that the schema for schemas is not actually
definitive (or normative) -- a problem, since the schema is _supposed_ to be. 

It would seem to me that this would have been an early hint that "choice"
should have applied to attributes as well.  Since this is not the case, what is
the standard way to implement selection between multiple mutually exclusive
attributes when creating a schema?

Also, what was the reason for not allowing choice to operate over attributes?

Is this a known problem with the supposedly normative schema for schemas and
the XSDL spec?

Back in the WD days, "fixed" and "default" were different values for the "use"
attribute, so this could be used to assert the mutual exclusivity.  Now that
they are attributes in their own right there doesn't seem to be any way to do
this.

Ian.

-- 
Ian Stokes-Rees                       DecisionSoft Ltd.
Telephone: +44-1865-203192            http://www.decisionsoft.com
Received on Friday, 20 April 2001 09:55:34 GMT

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