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Re: Update on namespaces

From: Peter Murray-Rust <Peter@ursus.demon.co.uk>
Date: Fri, 27 Jun 1997 08:48:18 GMT
Message-Id: <8552@ursus.demon.co.uk>
To: w3c-sgml-wg@w3.org
In message <199706270551.PAA30543@jawa.chilli.net.au> ricko@allette.com.au writes:
> 
> > From: Andrew Layman <andrewl@microsoft.com>
> 
> > Namespaces does not mean that suddenly any element is valid anywhere.
> > 
> > I absolutely am not suggesting that the use of namespace means that
> > every element suddenly has an implicit content model of "ANY".
> ...
> > That is, far from defeating validation, namespaces permit use of
> > multiple, merged schemata while retaining validation.
[...]
> 4) An SGML content model should allow a #OTHER keyword:  ANY is too
> fixed,
> and fully declared content models are too restrictive. E.g.
> 
> <!ELEMENT html ( head, (body | frameset | layer | #OTHER ), tail ) >
> 
> where #OTHER means you can only use an element from some other
> namespace. 

Both AndrewL and RickJ have proposed namespace philosophies which should be
supported.  Andrew's might be examplified by (say) a DTD for the J. Physical
Chemistry (a real journal), which might wish to publish in XML.  It could 
construct its own DTD based (say) on X-HTML, with precise contexts in which 
MathML and CML can be imported.  This may be workable with a very static
editorial policy where the style was frozen for some years.  The problem  is 
that  
(a) it can be difficult to identify all the places where merged content
is allowed (e.g. equations (math or chem) in tables, citations, etc.) 
(b) if a new mergeable DTD becomes important, it's extremely difficult to 
edit the DTD to include it.  You start running into n-squared numbers of 
interactions.  And, since CML may very well include (or interoperate with)
MathML, you may have unforeseen second-order problems.

Rick's position would seem to be the only way of creating a valitable approach
for a more general journal like Science or Nature, which range from Astronomy
to Archaeology.  (At present CML get rounds it by having a single container - 
XLIST - which has a content of ANY and can occur almost anywhere.  #OTHER makes
this approach more honest.)

	P.

-- 
Peter Murray-Rust, domestic net connection
Virtual School of Molecular Sciences
http://www.vsms.nottingham.ac.uk/
Received on Friday, 27 June 1997 04:37:13 EDT

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