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   Re: [xml-dev] On the promotion and demotion of information items (was Re

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From: "K. Ari Krupnikov" <ari@cogsci.ed.ac.uk>

> What's wrong with using PIs for that?

The files use comments. Different rave :-)

> Incidentally, some WXS experts might say that you want to allow any
> elements in namespaces other than yours at any position in the
> document, and attributes in other namespaces on any elements precisely
> because this allows "I don't know what it is but I included it anyway"
> information "anywhere" in the document.

Good point. 

But it is a bogus approach, because if the schema writer thought the
information was useful, they would have made the elements in the same

(It also may be a bogus approach because it is more likely that the recipient
will alter the schema to cope with their specific changes, and so the 
sender would pass the buck on openness to the recipient.)

The trouble is that it makes it the problem of the schema-writer to foresee 
that they missed something.  And human nature does not work like that IMHO.  

Also, in the current case we have start and end tags, so the schema language
would have to be able to support something like "promoting the descendents in
this namespace of all descendents in other namespaces of this element will result
in a content model that looks like this: ( add* )"   [1]
I think RELAX NG can do this kind of  thing a little (see the RELAX NG schema 
for RDF for example of anonymous layers), but only a madman would write  
a schema like that: highly complicated just to cope with interposed layers whose
justification is hypothetical at the time the schema was developed. 

Rick Jelliffe

[1] In Schematron you could use something like
   <rule test=".//*[namespace()=current*()/namespace()]
 to prefix the rules to cope with arbitrarily interposed elements in different namespaces,
I guess. Yuck.


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