Disjoint datatypes?

Can I build a datatype out of pieces that are disjoint? A simple example
might be US_states + Canadian_provinces. Say my schema already contains
declarations of these two enumerations. The new enumeration I want is the
merger of the two. I don't want to extend one with the members of the other,
explicitly written out.
A more complex case is SQL style datatypes: integer + NULL. Can I build such
a datatype in XSchema?
Thanks,
David
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Received on Wednesday, 3 May 2000 12:04:40 UTC