Access Control List (ACL)

• Each column stored as an access list of
  (domain, operation) stored with each object
• In Unix, for instance, only 3 user domains (owner/user (u) , group (g) and others (o)) - with operations being read (r), write (w) and execute (x)
• A file can be set to switch userid to owner when it executes i.e. allows increase of privilege when using system programs
• Unix approach gives very coarse ACL
• Explicitly storing domains or individual users is more flexible
• Systems with more explicit ACLs store default domains plus individual entries (VAX/VMS)

System		r		w		-

Owner		r		w		e

Group		r		-		e

World		-		-		-

joe		r		-		-

tom		r		-		e