Access right question in Oracle 7

A question about access right:

I want to have a single oracle instance (single database) to handle all student projects. I need to fulfill the following criteria:

1. For each project, the supervisor should have the right to access
   (select & update) all tables for all his/her project members.
   
2. Any project supervisor should not be able to access any other project tables.

Basically, everything is achievable if I grant each project member's table to the project supervisor. However, this will be very inconvenint. Any more automatic method for this? I have heard that creating a role
(like mgr), grant to the supervisor, and let him/her create the project
members can achieve this (something like inheritance), but I can't test it out successfully. Any idea about this?

Either mail or post is welcome.

Thanks a lot.

--
Tang Wai Shing, Wilson				email: cswstang_at_cs.ust.hk
Department of Computer Science, HKUST, HK	tel# : (852)-358-7004