external dtd subsets

II. please establish a method to bind a prefix which covers the internal and
external dtd subsets.

without such a mechanism, the dtd's denotation is undefined.

if, on the other hand, such a mechanism is provided, then validation is
possible on the basis of namespace-aware 1.0 conformant dtd's.

additional pseudo-attributes in the XMLDecl form would suffice.

please see my questions to xml-dev on this topic.
(http://www.lists.ic.ac.uk/hypermail/xml-dev/9808/0112.html, and
 http://www.lists.ic.ac.uk/hypermail/xml-dev/9808/0129.html)