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Re: Missing constraints

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 19 Nov 2002 20:06:27 +0000
To: sandygao@ca.ibm.com
Cc: w3c-xml-schema-ig@w3.org, www-xml-schema-comments@w3.org
Message-ID: <f5bu1idgw8s.fsf@erasmus.inf.ed.ac.uk>

sandygao@ca.ibm.com writes:

> There seem to be some rules that are implied by the spec (from some
> definitions, or description), but there is no constraint to enforce them.

That's not _ipso facto_ a bug - - the whole spec. is normative, not
just the constraints.  Having said that, I agree it is in general
desirable to have things that matter in the constraints.

> 2. <schema targetNamespace="">
> The spec says "Since the empty string is not a legal namespace name,
> supplying an empty string for targetNamespace is incoherent, and is not the
> same as not specifying it at all." Does this imply the above is invalid? Or
> still valid? If it's valid, what would be the target namespace of
> components defined in this schema?

Not valid.

> 5. xsi:schemaLocation has odd number of URI's
> "xsi:schemaLocation" is a list of anyURI. Each 2 of such anyURI's make a
> pair: one indicates the namespace, the other is a location hint. What
> happens if this attribute has an odd number of items? Is it an error? Or
> should the processor silently ignore the last item in the list?

There should be a normative statement about this, you're right.

> 6. Target namespace doesn't match xsi:schemaLocation or
> xsi:noNamespaceSchemaLocation
> What happens if the schema location hint points to a schema document with a
> target namespace different from what's expected? For example, what happens
> if the instance has
>   xsi:schemaLocation="ns1 a.xsd"
>   xsi:noNamespaceSchemaLocation="b.xsd"
> but a.xsd has a target namespace not identical to "ns1", or b.xsd has a
> target namespace? I suppose these are error situations, but no constraints
> are defined.

Again, there should be a normative statement for this, eys.

> 7. Undeclared entities
> The definition of the "ENTITY" type says "... The ·value space· of ENTITY
> is ... and have been declared as an unparsed entity in a document type
> definition. ..." But no constraint is defined to support this rule.

That's coming in an erratum, see [1].

> 8. Undeclared namespace prefixes
> The note under the definition of the "QName" type says "NOTE: The mapping
> between literals in the ·lexical space· and values in the ·value space· of
> QName requires a namespace declaration to be in scope for the context in
> which QName is used." But the spec didn't say what happens if there isn't
> such a namespace declaration.

Again, erratum coming, can't find the reference -- Paul?


[1] http://www.w3.org/2001/05/xmlschema-rec-comments.html#pfiENTITY
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2002, 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/
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Received on Tuesday, 19 November 2002 15:06:29 UTC

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