> But again, this is confusing namespace and definition; isn't it?
> Regardless of how you do the namespaces, the definitions will need
> different names if they are different.

No!   Currently, as mods and mads have separate namespaces, in a mods
instance you have <name> and in a mads instance you have <name>,  neither
needs a prefix because they are implicitly qualified, and they mean
mods:name and mads:name respectively.

(There is an analogy in SRW indexes:   dc.description and ccg.description
are two SRW indexes with the same name (description), qualified by their
index set (dc vs. ccg) and with different definitions.)

> ... in RNG, you can have a base definition in your library, and then
> redefine it on import.   You can see a MODS-related example here, where
> I include mods in docbook, but redefine the mods extension element to
> allow docbook content (for editing support):
> why-i-like-relax-ng
> Can you not do that in XSD?

I'm going to try to work with this some more.