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Re: XML Schema working with DTDs?

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 01 May 2000 21:42:20 +0100
To: "Joseph M. Reagle Jr." <reagle@w3.org>
Cc: Noah_Mendelsohn@lotus.com, cmsmcq@acm.org, <xmlschema-dev@w3.org>, www-xml-schema-comments@w3.org
Message-ID: <f5bvh0yypcj.fsf@cogsci.ed.ac.uk>
"Joseph M. Reagle Jr." <reagle@w3.org> writes:

> Found it, I knew that I saw it before:
>   2.6.3 xsi:schemaLocation, xsi:noNamespaceSchemaLocation
>   The xsi:schemaLocation and xsi:noNamespaceSchemaLocation attributes 
>   http://www.w3.org/TR/xmlschema-1/#xsi:schemaLocation
> 
> So including these attributes in the schema for schema example in the spec
> would be helpful.
> 
> >At 09:27 2000-04-29 -0500, Dan Connolly wrote:
> >BTW: Has there ever been any consideration in schema (I thought I saw this
> >but don't see it presently) to include a location attribute in the schema
> >element type? If a namespace need not be dereferencable (like PUBLIC) then
> >wouldn't it make sense to include a SYSTEM as well?


I'm confused by the above extracts, perhaps the context would have
clarified things.

SYSTEM and PUBLIC are part of the mechanisms by which an XML instance
points to external entities, in particular to (the external subset of) 
DTDs.

The analogous aspects of XML instances for schemas are
xsi:schemaLocation and xmlns, where xsi is declared as
http://www.w3.org/1999/XMLSchema-instance.

You can put a schemaLocation attribute from that namespace on any
element in any document without it needing a declaration.

There's a lengthy discussion of all this in section 3 of chapter 6 of
the spec. [1].

I'm slightly at a loss to know exactly what you are asking for -- are
you suggesting that the schema for schemas should be modified to
include a namespace declaration for
http://www.w3.org/1999/XMLSchema-instance.and a schemaLocation
attribute from that namespace?  We could do that, but since the schema
which applies to the schema for schemas, which is of course itself
(:-), actually _does_ live at its namespace URI, there didn't seem any 
point.

I'm also perplexed by the analogy with SYSTEM and PUBLIC, in that in
vanilla XML 1.0, you  _don't_ find those inside DTD documents at all.

But maybe that's not what you meant.

ht
-- 
  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/
Received on Monday, 1 May 2000 16:42:42 GMT

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