help needed regarding Query processing in postgres

hi all,

I am an M.Tech student of IITBombay,india.
We are doing a project on access control in postgres.

Is there any way in which, i can add a extra predicate to the sql query
given to the postgres database table.

please if any body could help me in this regard. Reply as soon as posible.

thanks and regards.
kiran

KReSIT , IITB.