Q re columns accessible from INSERT/UPDATE VPD policy predicates

Hello everyone,

the policy predicates returned from VPD policy functions are said to be "appended as a WHERE clause" to any DML operation on the table protected by that policy. The predicates may access columns of the protected table by simply naming them. This is easily understood with SELECT operations (just imagine the standard example of "... WHERE owner = USER" accessing the owner column) and DELETE operations, but what about UPDATE and INSERT?
May the columns of the row to be updated or deleted be accessed, and if so, how? Perhaps using :OLD resp. :NEW qualifiers as in triggers?

I searched Oracle online docs and AskTom, to no avail (and may experiments ran into problems which I'm not sure are related to my question here).

Thanks for your help,
Holger.

-- 
Dr. Holger Peine
Fraunhofer IESE, Kaiserslautern, Germany
Phone +49-6301-707-134, Fax -209 (shared)
www.iese.fraunhofer.de/Staff/peine -- PGP key on request or via pgp.mit.edu