xml-dev - Re: Canonicalized Schemas

[ht@cogsci.ed.ac.uk (Henry S. Thompson)]

"Simon St.Laurent" <simonstl@simonstl.com> writes:

> Is it possible to transform an XML Schema into Canonical XML and still be
> able to use the Schema?
> 
> It seems to me that it isn't, unless the application has some other kind of
> access to the namespace prefix-URI mappings that are discarded by
> Canonicalization (c14n).  The prefixes will live on in the attribute
> values, but the prefix-URI mapping will disappear.
> 
> This could suggest a few possibilities:
> 1) Canonical XML is not intended as a transfer format - the only reason it
> exists is to establish a common form that can be used in conjunction with
> digital signatures.  While Canonical XML suggests a document syntax, that
> document syntax is only metaphorical, and not intended for actual transfer
> over the wire.

I don't know if it's meant to be a transfer format or not.  I observe
that the crucial think about c14n for schemas is that if two schemas
differ only in the prefixes they use, their canonicalisations should
be identical.  Not necessarily still valid schemas, just identical.

> 2) The Schema and c14n groups (and others, including XLink and perhaps
> XPath) need to have a discussion about what exactly 'namespace-aware'
> processing involves, and the role of prefixes within that processing.  This
> could lead to some form of prefix preservation within c14n.

Yes we need to coordinate, for sure.  Not, in my view, to achieve
prefix preservation, but to get c14n sensitivity to QName
declarations.

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/

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