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Re: [xml-dev] which xml schema tools do it right concerning including attributes xml:lang and xml:space

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 19 Apr 2002 10:27:48 +0100
To: "Dare Obasanjo" <dareo@microsoft.com>
Cc: "Paul Hermans" <paul_hermans@protext.be>, <xml-dev@lists.xml.org>, <xmlschema-dev@w3.org>
Message-ID: <f5b1ydcm417.fsf@cogsci.ed.ac.uk>
"Dare Obasanjo" <dareo@microsoft.com> writes:

> *sigh*
> 
> After confering with some of our schema folks something was brought
> up which adds a caveat to my comments.
> 
> A problem arises because the normative schema for Schema (sForS)
> imports the schema for the XML namespace already. This means that a
> conformant XSD implementation acts as if the XSD for the
> "http://www.w3.org/2001/XMLSchema" and
> "http://www.w3.org/XML/1998/namespace" were imported into any schema
> it validates. However, Paul is attempting to re-import that
> namespace using a different schemaLocation and XSD. According to the
> W3C XML Schema recommendation[0]
> 
> "NOTE: The above is carefully worded so that multiple <import>ing of
> the same schema document will not constitute a violation of clause 2
> of Schema Properties Correct (§3.15.6), but applications are
> allowed, indeed encouraged, to avoid <import>ing the same schema
> document more than once to forestall the necessity of establishing
> identity component by component. Given that the schemaLocation
> [attribute] is only a hint, it is open to applications to ignore all
> but the first <import> for a given namespace, regardless of the
> ·actual value· of schemaLocation, but such a strategy risks missing
> useful information when new schemaLocations are offered."
> 
> So this means it is possible for a conformant implementation to
> ignore a schema author's attempt to re-import the XML namespace and
> redefine its components. Currently the Microsoft .NET implementation
> does this but does not issue any warning when it does.
> 

XSV does the same, i.e. it only fetches one schema document per
imported namespace, regardless of how many <import> elements it
encounters.

ht
-- 
  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 Friday, 19 April 2002 05:27:52 GMT

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