Uniqueness constraint over multiple attributes

[Jan Beerden <jan.beerden@fks.be>]

Hello,

Is there a way to have a unique constraint over multiple attributes? We 
have different attributes for the primary email address of a person, and 
for additional aliases, and we'd like to enforce global uniqueness in 
such a way that the primary email address for one person can not be used 
as an email alias for another person.

The slapo-unique manpage doesn't make this very clear.

Regards

--
Jan Beerden                                   jan.beerden@fks.be
fks bvba - Formal and Knowledge Systems       http://www.fks.be/
Schampbergstraat 32                           Tel:  ++32-(0)11-21 49 11
B-3511 Kuringen                               Fax:  ++32-(0)11-22 04 19