Right the old "DTD vs DTD" trick (I remember this being a trick
question I was casually asked to see if I was "in the know" by
someone who shall remain nameless.).
> The notation of a vocabulary is quite useful, I think, when
> talking about namespaces in XML. XML namespaces are basically a means of
> collisions in vocabularies. Namespaces solve the problem of combining
> vocabularies, not the problem of combining DTDs.
The problem I have with XML namespace is that it is really little more
than alpha renaming: kind of like the elisp idea of adding a package
prefix (Java kind of does the same thing).
The *real* problem is still one of matching ontologies. EDI/B2B is a
case in point, where the desire is not to reuse partial vocabularies
at all. XML namespaces do little here that could not have been accomplished
via other means (attributes etc).