Norman Walsh wrote:

[bunch of sensible stuff deleted]

>  Extending DTDs to work outside this environment, by means of a PI for
>  example that mapped prefixes to URIs in the DTD, would make a parser
>  that accepted documents that were not XML 1.0 valid but were XML
>  1.0+Namespaces valid. It'd be an interesting exercise.
> 
The problem is that for the internal subset, no mapping is needed because
the prefix-> URI mapping can be obtained from the content context. The
problem exists for external DTDs which could use a PE to 'substitute' the
{file://foo}aaa notation for the xxx:aaa notation, if this notation were
adopted as part of the DTD syntax.

i.e.

[
<!ELEMENT root (xxx:aaa)* > 
]
<root xmlns:xxx="file://foo" xmlns:yyy="file://foo" > 
    <xxx:aaa/> 
    <yyy:aaa/> 
</root> 

would be namespace valid.

Alternatively:

<!ELEMENT root ({file://foo}aaa)*> 

would allow definition of expanded names even in an external subset.

Jonathan Borden
The Open Healthcare Group
http://www.openhealth.org