PAM Authentication but different Jabber-ID maybe kind an alias

Hi

Iam using ejabberd with pam authentication. The Problem is that some logins im pam differ from the jabber-ids the user wants. Is there a was to say the jabber-id user1 belongs to the pam-id user2 and then authenticate against that ?

So im looking for a kind a user alias or user mapping, is this possible ?

Thanks Kev