defining attributes of xsd:string?

Not entirely sure this is the best list for this question, but...:

Suppose I want to define additional attributes of string -- 'additional' i.e.
with respect to such things as xml:lang.  For instance, I may want an
attribute that applies only to strings that are acronyms (in a given
language), or only to strings that are used as person's given names and
such.  Can I define these in my owl ontology? Or do I define them in a xml
schema and then somehow make them available in the ontology (and how would
this go, exactly)?

Grateful for suggestions.  Thank you,

-- 
# Pierluigi Miraglia pierlu.m
# Austin, Tex.