Cycoda: UML Use Case

Use Case Diagram

A use case diagram is a behaviour diagram that shows a set of use cases and actors and the relationships among them.

A use case represents a coherent unit of functionality provided by a system, a subsystem, or a class as manifested by sequences of messages exchanged among the system (subsystem, class) and one or more outside interactors (called actors) together with actions performed by the system (subsystem, class).

An actor defines a coherent set of roles interacting with a system. An actor may be considered to play a separate role with regard to each use case with which it communicates.