Use Case Diagram Example: External System as Actor

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Types of Actor in a Use Case Model

Actors in use case modeling can be people, other systems, temporal triggers, or event triggers.

  • An actor specifies the role played by a user or any other system that interacts with the subject. It can represent a role played by a human user, external hardware, or other subjects.

  • Actors are always outside the system, interacting directly with the system by initiating a use case, providing input to the system, and/or receiving output from the system.

  • An actor does not necessarily represent a specific physical entity, for example, a timer that triggers the sending of an email alert.

Primary vs Supporting Actors

  • Primary Actor: a user whose defined user goal and is fulfilled by the system

  • Supporting Actors: a user who provides a service (e.g., information) to the system.

Non-Human Actors

We often miss key personas during the use case mapping process because they only identify human actors. For non human actors we can identify:

  • System/Software

  • Hardware

  • Timer/Clock

Related Article

Use Case Analysis: How to Identify Actors?

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