NAMESPACES: expressing commonality or distinction

roddey at roddey at
Tue Sep 7 23:35:55 BST 1999

>and allow applications to match
>depending on what they care about
>PRO: uses existing namespace mechanism
>CON: would require modification to XPath, etc.

It would definitely have performance implications. It would no longer be
possible to put elements/attrs into pools and identify them by a pool id that
can be very efficiently checked and validated. I would be very concerned about
it from that perspective. If an element is no longer uniquely identified by
URI:Name, then it cannot be internally uniquely identified either.

And I wonder if saying "its an application thing" is going to float either. Many
apps will rely on tools to do a lot of work for them (otherwise XML will have
missed a big part of the boat), so all those tools would have to understand this
scheme or the apps that need this kind of functionality wouldn't be able to use
them very effectively perhaps. But how would you efficiently implement this kind
of thing in general purpose tools? For example, how would a DOM tree diff tool
handle such a thing so that only meaningful diffs to the application at hand
would show up?

I'm sure it could be done, but the question is it worth going down this road or
just forcing all apps that need to do this to have effectively their own
validation mechanisms, attribute uniqueness checks, and so on?

Dean Roddey
Software Weenie
IBM Center for Java Technology - Silicon Valley
roddey at

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