Issue: nsName using prefix

If you are writing a schema using multiple namespaces, you can declare a
prefix for each namespace once using a normal namespace declaration and then
use QNames to refer to names from each of the namespaces.  However, there is
currently no comparable facility with <nsName/>; there is no way to say
match any name whose namespace is the the namespace bound to prefix "x".
Should we add a way to do this?

James