Who needs XHTML Namespace?

David Brownell david-b at pacbell.net
Wed Sep 1 01:49:59 BST 1999

Paul Prescod wrote:
> David Megginson wrote:
> >
> > While we're still a ways away from having schemas that allow
> > document-type assembly from other schemas, the most important task for
> > XHTML (other than saying that XHTML should be well-formed XML, which
> > is a bit of a truisim), is to establish an XHTML Namespace so that
> > processors can discover HTML markup in arbitrary XML documents.   We
> > don't need Namespace-aware schemas or anything else to do that.
> What is the virtue in discovering XHTML data in an arbitrary document if
> there are *no rules* about what that information will look like?  Are you
> really going to write processors that do not care whether images occur
> within titles or tables within images?

Where does "no rules" come from, though?  I think the argument is
just that the choice of rules has no business being tightly coupled
to the element (and attribute) vocabulary being used ... the rules
get provided separately, by choice of DTD or schema.  We know that
in the future composite vocabularies are coming.  If each different
set of rules gets its own namespace ID, applications have a rather
significant combinatoric explosion to suffer through; bad design.

Consider a chunk of "strict" XHTML (sans namespaces).  It can be
validated using any of three DTDs.  There's no benefit from doing
any early binding of the elements to a "strict" namespace; the
next component doing the processing may need to add a frame.
That logic extends to other cases.

What's the virtue in coupling the semantics of a "p" element to one
of the several grammars which discuss its use?  If there is one, I've
not yet seen it described.  On the other side of the argument, not
buying into a combinatoric explosion in the number of namespace
identifiers seems virtuous to me.

- Dave

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