User Classes
In Unix : ordinary file : R, W, X privileges
directory : R, W, X (search for name and execute file)
Superuser (root) has over-riding permission to access in any mode
OwnerID can be substituted for userid for execute access to files -
change protection domain e.g. to allow user to execute a system utility
with system capabilities
List of Users
e.g. VAX/VMS : record - username, access mode (R, W or E)
There are other variations to these models, for instance, the concept of DOMAINS in WinNT - we shall cover these in Security later