Use case diagram is used to present in a graphical manner the functionality of a system. Use cases are the goals of an actor or the functions that an actor carries out. By the use of this diagram, functions of a system that are to be performed by an actor can be specified.
The above figure is a use case diagram that presents the enrollment system of the university. Use cases are represented by ovals and the actors are represented by stick figures. The connecting lines between an actor and a use case represents as the association to show that an actor carries out a use case. The figure shows the use cases that a student should perform for him/her to be officially enrolled and the other actors who are involved in the system.
