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Re: HTML WG last call remark (no way to declare entities?)

From: Roger Bishop Jones <rbjones@rbjones.com>
Date: Thu, 6 Jul 2000 15:36:20 +0100
Message-ID: <000501bfe757$b00bd640$d358fd3e@roger>
To: "XML-schema-comments" <www-xml-schema-comments@w3.org>
This is a correction to my own recent posting on this topic.

When I wrote my message I had the wrong end of the stick about what XML 1.0
says about well-formedness, and this helped me to misread the explanation of
why entity definitions cannot be supported which was quoted by Dan Conolly
in his message.

Getting this straighter doesn't have much effect on my position, but it
certainly changes the way to describe it, so here's a revised attempt.

The definitions both of validity and of well-formedness in the XML 1.0
specification make reference to the DTD, and this presumption that there is
a DTD is a minor issue for the formulation of XML schema.
In relation to validity the approach of XMLschema appears to be to define a
new kind of validity, "schema-validity".
Given that this approach is taken to validity the obvious course in respect
of well-formedness would be to define "schema-well-formedness" giving the
minor adjustments to the notion of well-formedness that are appropriate to
XML documents which use schemas instead of DTDs.

Talking about "schema-well-formedness" may sound odd when the schema is
supposed to define validity rather than well-formedness, but this just
carries forward the historical situation in relation to XML 1.0 that the
content of the internal subset of the DTD, and the existence (or otherwise)
of an external subset (or at least the value of a "standalone" attribute)
plays a role in the definition of well-formedness.

The definition of "schema-well-formedness" would be exactly the same as that
for well-formedness, except that references to the internal or external
subset of the DTD are replaced by similar references to the schema.

This is very similar to the definition in the quoted passage of Dan
Conolly's message of "nearly well-formed".
Except that, if I understand it correctly (which is doubtful) this is
offered as a part of a reason for not allowing schemas to include
definitions of parsed entities, whereas, as far as I can see, it is a
satisfactory resolution of any supposed conflict between XML 1.0
well-formedness and the support by XML schema of entity definitions.

Once again I come to a request for a fuller explanation of why there is a
problem, for, apart from the need for a minor adjustment to the notion of
well-formedness which flows naturally from the use of schemas instead of
DTDs, I don't see one.

Roger Jones
Received on Thursday, 6 July 2000 10:40:25 UTC

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