The basic function of any access control system is to monitor the opening and closing of the doors. There are 4 process that any access control system employs to be effective in its purpose. Identification, Authentication, Authorization and Accountability.
The identification gathers information about who is requesting for an access. Authentication is accomplished by methods designed to prove or disapprove the identification information. Authorization consists of a set of rules that define who can enter and under what circumstances. Finally, Accountability is the process of logging and reporting not only who has requested access and the results of that request, but also who has created the Authorization rules that are applied.