Introduction :
- A use case diagram describes how a system interacts with outside actors.
- It is a graphical representation of the interaction among the elements and system.
- Each use case representation a piece of functionality that a system provides to its user.
- Use case identities the functionality of a system.
- A use case diagram contains four components :
I. The boundary, which defines the system of interest in relation to the world around it.
II. The actors, usually individuals invoked with the system defined according to their roles.
III. The use cases, which the specific roles are played by the actors within and around the system.
IV. The relationship between and among the actors and the use cases.
Purpose :
- The main purpose of the use case diagram is to capture the dynamic aspects of a system.
- Use case diagram shows, what software is suppose to do from user point of view.
- It describes the behavior of system from user's point.
- It provides functional description of system and its major processes.
- Use case diagram defines the scope of the system you are building.
When to Use : Use Cases Diagrams
- Use cases are used in almost every project.
- They are helpful in exposing requirements and planning the project.
- During the initial stage of a project most use cases should be defined.