Q. Researchers have recommended that instead of having an access list associated with each file (specifying which users can access the file and how) we should have a user control list associated with each user (specifying which files a user can access and how). Examine the relative merits of these two schemes.

Answer:

• File control list. Because the access control information is concentrated in one single place it is simpler to change access control information and this requires less space.
• User control list. This needs less overhead when opening a file.