Re: NVDL

Norm Walsh writes:

> NVDL is designed for namespace-based dispatching so it follows 
> that it's a solution that can only be considered when different
> versions appear in different namespaces.

Yes, exactly, and there are many situations in which such 
namespace-dispatching is natural and desirable.  That said, I would prefer 
that the TAG not appear to imply that such namespace-based composition of 
vocabularies is the only one that's ever sensible.  Note that I am >not< 
suggesting that one avoid using namespaces;  I think it's almost always 
desirable to NS-qualify one's XML elements, and in some cases attributes 
as well.  I am saying that there are cases in which one wishes to 
modularize markup in ways that are not best modeled as namespace-driven. 
For example, one might in some organization use a handful of namespaces 
for abstractions such as inventory, monetary abstractions, etc., and then 
assemble schemas for particular document formats such as purchase orders 
by quite freely mixing bits of markup from these namespaces.  In such 
cases, I think it's often more appropriate to suggest that the root 
element name (not just its namespace) indicates the nature of the document 
as a whole, with namespace-qualified markup mixed quite freely inside.

I'm not an NVDL expert, but my impression is that it's not focussed 
primarily on such idioms.  In summary, I have no problem pointing to NVDL 
as an example of good practice for the things it does well;  I would like 
to avoid appearing in so doing to discourage use of languages in which 
different versions share a namespace, or in which the same version of a 
language freely mixes bits from many namespaces.

Noah

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Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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Received on Thursday, 19 July 2007 22:07:20 UTC