Question for XMLHeads - can an XML DTD refer to a remote XML document as a resource?

If it can, could we solve the lexicon problem (which is, that some people like the idea of a lexicon and others don't) like this?

A lexicographer puts onto the web an XML resource that provides a character/state list for a given universe of interest (seed plants/all life/the flagellated sporozoans of deepsea hydrothermal vents, whatever). If other workers like the character list and think they can live with it, then they include a URL to the lexicon in their document, and the lexicon is used as their character list. But if no available lexicon works for a given user, then they can define their own character list. That way, perhaps we'll all be happy.

If this model works, it could perhaps also allow for extensibility ie mixed lists comprising remote lexica and extra document-defined characters.

A problem with such lexica would be data security - what would happen if the lexicon's server crashes permanently - and how to allow for evolving lexica without invalidating previous treatments.

Any good?

Cheers - k