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The requirements define the formal functional requirements that a use case must supply to the end user. The uses connector can optionally have multiplicity values at each end, as in the following diagram, which shows a customer may only have one withdrawal session at a time, but a bank may have any number of customers making withdrawals concurrently.Ī use case is normally named as a verb-phrase and given a brief informal textual description. The following diagram indicates that the actor "Customer" uses the "Withdraw" use case. The notation for using a use case is a connecting line with an optional arrowhead showing the direction of control. The notation for a use case is an ellipse. It provides a high-level view of behavior observable to someone or something outside the system. An actor is usually drawn as a named stick figure, or alternatively as a class rectangle with the «actor» keyword.Īctors can generalize other actors as detailed in the following diagram:Ī use case is a single unit of meaningful work. Actors represent roles which may include human users, external hardware or other systems. These external entities are referred to as actors. Use cases are a means of communicating with users and other stakeholders what the system is intended to do.Ī use case diagram shows the interaction between the system and entities external to the system. The use case model captures the requirements of a system. UML 2 Tutorial - Use Case Diagram Use Case Diagrams