Comment on Associating Schemas with XML documents 1.0 (First Edition) - type handling

This is a comment on the editor's draft of Associating Schemas with XML 
documents 1.0 (First Edition) [1]. 

The draft provides both an href pseudo-attribute, and also an explicit 
Type pseudo-attribute with the description:

"Specifies the content type of the referenced schema. If unspecified, the 
xml-model processor should return a parsing result that would be identical 
to that when the value is given as application/xml."

As discussed in the applicable RFCs and the TAG's finding on Authoritative 
Metadata [2], any Content-type returned with status code 200 from an HTTP 
GET is authoritative, regardless of what might be specified in a Type 
pseudo-attribute.  Accordingly, I think it would be appropriate for the 
Associating Schemas document to deal explicitly with the case where the 
authoritative metadata contradicts the explicitly specified type.  I think 
that acceptable approaches would include:  making that a runtime error; 
silently accepting the authoritative type, and thus ignoring the one 
specified in the PI;  accepting the authoritative type, but suggesting 
that a warning might be appropriate if the processor has a way of 
reflecting it.

BTW: I am copying this suggestion to www-tag, but I am writing as an 
individual.  The TAG has not at as a group considered the Associating 
Schemas draft.  Thank you.

Noah

[1] http://www.w3.org/XML/2010/01/xml-model/
[2] http://www.w3.org/2001/tag/doc/mime-respect-20060412

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Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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Received on Thursday, 4 February 2010 22:54:43 UTC