Namespaces hate validation!

Ronald Bourret rbourret at
Thu Jan 7 10:45:52 GMT 1999

Murray Maloney wrote:

> Well, I just looked at XSchema again, and while it does include
> some facilities for namespace-awareness, it is not clear to me
> that it integrates "Namespaces in XML".
> In a fact, I have to challenge your assertion that XSchema
> integrates with "Namespaces in XML". Quoting from XSchema (4.3.2):
> The following XSchema structures cannot be converted
> to DTD structures because such structures do not exist:
> [structures and other stuff snipped]
> >DCD almost does this, but is silent on how it associates namespace 
> >used in attribute values (such as the name of an element being declared) 
> >with URIs.
> So, DCD does not integrate with "Namespaces in XML".
> [snip]
> >In any case, it is certainly possible to integrate the current namespace 
> >proposal with a schema language, as XSchema shows.
> XSchema shows no such thing as section 4.3.2 makes clear.

The impossibility of converting XSchema structures (even if they are rel  
ated to namespaces) to DTDs has nothing to do with namespace support in 
XSchema -- it has to do with converting XSchema documents to DTDs.

XSchema and DCD (as soon as a prefix=>namespace URI associator is added) 
both completely support the current namespaces spec. That is, they provide 
enough namespace information that an application, parser, whatever, can 
look at a schema document and determine the namespace to which an element 
or attribute belongs.

One important consequence of this is that the problem that started this 
entire discussion -- validating a namespace-using instance document against 
a DTD -- can be performed.  That is, a namespace- and schema-aware parser 
(or namespace and schema layers on top of existing parsers) can take a 
document that uses namespaces and its associated schema document and 
validate that document against that schema.  If this is not possible, then 
it is a bug in XSchema or DCD and needs to be fixed.

-- Ron Bourret

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