Use Case Diagram

Learn about the use case diagram and its benefits with some examples.

Use case diagram describes the specification of users and their possible interactions with the system. These possible interactions are called use cases.

Components of a use case diagram

To understand a use case diagram, it is important to first understand its components. Use case diagrams have the following components:

  • Actor: Users are called actors. They interact with the system. They could be humans, machines/hardware, or other external systems. There are two types of actors:

    • Primary actors: These are the humans or external systems that interact with that system and are responsible for initiating the use case. They are placed on the left side in a use case diagram. Primary actors are also called active actors.

    • Secondary actors: These are the ones that are used by the system to assist the primary actors in a use case. They cannot interact with the system on their own. They need primary actors to initiate a use case. Secondary actors are also called passive actors, and they are placed on the right side in a use case diagram.

  • Use case: This is a single function performed on a system by an actor. It is represented by an oval shape.

  • Package: This is a group of different elements. These groups are represented inside a folder icon.

  • Note: This is used to add additional information about any component or relationship in a use case diagram.

The representation of the components explained above in a use case diagram is given below:

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