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   Re: Namespaces and Schemes

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  • From: ht@cogsci.ed.ac.uk (Henry S. Thompson)
  • To: "Sean B. Palmer" <sean@mysterylights.com>
  • Date: Wed, 29 Nov 2000 10:02:48 +0000

"Sean B. Palmer" <sean@mysterylights.com> writes:

> > I encourage you to read the XML Schema Primer [1], which contains a good
> > introduction to the mechanisms by which you can associate schemas with
> > namespaces -- putting a schema document at the namespace URI is only
> > one of them.  I think there's enough flexibility in the spec. to
> > accommodate your needs.
> According to 6.3.2(2):-
> "The author of a document uses namespace declarations to indicate the
> intended interpretation of names appearing therein; there may or may not be
> a schema retrievable via the namespace URI."
> Can we simply declare a namespace for a document then, and validate it using
> that namespace as a Schema URI? Is that legal? There seems to be some
> abiguity in that statement "may or may not be".

To summarise the XML Schema design in this area:

  The connection between instance and schema can be established in a
  number of ways:

   1) An application may have a schema built in, and always use that one;
   2) An application may allow a user to provide one or more schema
      documents, e.g. on the command line, for use in validation;
   3) An instance may contain
      attributes, which in turn associate namespaces with the location 
      of schema documents for that namespace, and an application may
      exploit this to find those documents;
   4) An application may attempt to dereference namespace URIs and use 
      schema documents found as a result.

   The XML Schema draft spec. does _not_ mandate a particular order in
   which these strategies should be followed, if more than one is
   supported, but does encourage processors to support all of (2) -- (4).

  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, 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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