The main purpose of a use case diagram is to show the entities interact with your system, and the main goals they achieve with it. Create Actors to signify classes of people, organizations, other systems, software or devices that communicate with your system or subsystem. Asignificant part of the Unified Modeling Language (UML) is the competence for drawing use case diagrams. Use cases are used during the analysis phase of a project to classify system functionality.

• To hold Functional Requirements in an easy to read and tracking format.
• To represent the goal of an interaction between an actor and the system.
• Being multi-level, one use case can use/extent the functionality of another.