Use Case Diagram (UML)

Use case diagram consists of use cases, actors and relationships among them. It presents a user interaction with the system and defines the specifications of use cases.

Software Ideas Modeler offers tools for following elements of a use case diagram:

  • Actor
  • Use Case
  • Collaboration
  • Association
  • Include
  • Extend
  • Generalization
  • Realization
  • System Boundary


An actor represents a role in a system. It is not a specific user or person. It can be a human role, an external system or an application.


Use Case

An use case represents functionality of an analyzed system, it captures a requirement. It defines interaction between a role (actor) and a system. It specifies actions which lead to achieving a goal.

Use Case

Use case has these parameters:

  • Name
  • ID
  • Brief description
  • Primary Actor
  • Scope - it can be organization black box, organization white box, system black box, system white box or component
  • Level - it can be very high summary, summary, usergoal, subfunction or too low
  • Precondition
  • Postconditions
    • Minimal guarantees
    • Success guarantess
  • Triggers
  • Frequency of use
  • Priority
  • State - it can be draft, review, final or cancelled


An extending use case extends the behaviour of an extended use case. The extended use cases is dependant on the extending use case. Extend allows you to define a extension point, which refers to the step in the flow where the use case is extended.

The arrow of this relationship points from an extending use case to an extended use case.

Extended Use Case


An including use case is dependant on an included use case. The included use case is a mandatory part of the including use case.

The arrow of this relationship points from an including use case to an included use case.

Inluded Use Case

System Boundary

System boundary is a rectangular area which helps you to divide use cases into visual groups.

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