I don't think I understand your question thoroughly. form-based authentication is just that, the container just checks against your roles, users, realm, etc; but that's about it.
if you need to fetch additional information from that user, I guess you'll have to go an look it up in the database.
maybe I'm the only one not fully understanding your question...
[ January 06, 2004: Message edited by: Andres Gonzalez ]