Namespaces and XML validation

John Cowan cowan at
Fri Aug 7 19:08:15 BST 1998

Tim Bray scripsit:
> As for the syntax problem.  Let's assume we've got a compound DTD, and
> know, for each name in there, what namespace it comes from.

The draft, to be sure, mentions no such method.  But we can suppose
that this proto-DTD contains PIs, let's say the PIs from the old
draft, that tell us what the namespaces are, or it could just be
verbose but simple PIs that say:

	element A belongs to namespace foo
	global attribute B belongs to namespace bar
	attribute B of element A belongs to namespace baz

> So you take one pass through the instance, observing which namespace
> URIs are in play.  You make a unique prefix for each.  You take another
> pass through the instance, declaring all the prefixes on the root
> element, and eliminating all defaults, so that everything is prefixed,
> and that the same prefix is used for each namespace in all cases.  Then
> you go back and munge the DTD, inserting the same namespace
> prefixes on all names as appropriate.  Then you validate.
> Hey-presto!

Okay.  So you can validate provided you are willing not only to
rewrite the DTD (which is reasonable) but to rewrite the instance
too!  That concedes in effect that there are instances which
simply *cannot* be validated, because they use the same QNames
in inconsistent ways.  There may be other instances, equivalent
wrt namespaces, that can be validated, but that's not the same thing.

(2nd response follows wrt the semantic problem)

John Cowan		cowan at
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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