Use Case

A use case is a sequence of events (transactions) performed by a system in response to a trigger initiated by an actor. A use case contains all the events that can occur between an actor-use case pair, not necessarily the ones that will occur in any particular scenario.

In its simplest form, a use case can be described as a specific way of using the system from a user's (actor's) perspective. A use case also illustrates:

• A pattern of behavior the system exhibits.
• A sequence of related transactions performed by an actor and the system.

Use cases provide a means to:

• Capture system requirements.
• Communicate with the end users and domain experts.
• Test the system.

Use cases are best discovered by examining what the actor needs and defining what the actor will be able to do with the system; this helps ensure that the system will be what the user expects.

Since all the needs of a system typically cannot be covered in one use case, it is usual to have a collection of use cases. Together this use case collection specifies all the ways of using the system.

A use case may have a name, although it is typically not a simple name. It is often written as an informal text description of the actors and the sequences of events between objects. Use case names often start with a verb.

The name of the use case is displayed below the icon.