How to assert equivalence of URIs ?

Hi everybody,

Is there a way to assert that two URIs are equivalent ?

In owl, sameAs allows to specify the equivalence of two individuals,  
but when applied to classes this would make the ontology OWL-full.

In any case I would like to assert that two URIs, no matter their  
meaning, are the same.
Let's say I'm defining these URIs, and for "legacy" reason I have two  
different "spellings". How should I deal with this situation ?

best,
Andrea Splendiani