Use Case Diagrams: Actors, Goals, and System Boundaries

Understand actors and user goals before adding include or extend relationships. A small submission-system example keeps scope distinct from workflow.

Open the Use Case Diagram Generator to draft the visual, then use the topic-specific checks below to review it.

Original AI-generated use case diagram teaching reference. Simplified for explanation; review labels and relationships before use.

Start from goals rather than screens

Submit a manuscript is a goal; click a button is an interface action. Give the use case diagram generator the external roles and outcomes the system supports. Keep screen names and internal service calls for a different view.

Name the boundary explicitly

The same organization can be inside one system model and outside another. A boundary label explains what the diagram includes. An actor is a role in the interaction, so one person can play more than one role without requiring the roles to be merged.

Use include and extend sparingly

Plain actor associations are often enough for a scope overview. Include describes reused required behavior, while extend adds conditional behavior to a base case. Neither relationship should be used just to arrange ovals or to show chronological steps.

Reference key

Mistakes to check

Putting internal components outside as actors

A database inside the modeled system is not an external actor just because it has its own icon.

Using associations as a flowchart

A plain line indicates participation. It does not tell readers which goal happens first.

Reversing include and extend

Check the target of each dashed arrow and the intended semantics rather than choosing a familiar-looking label.

Use a short narrative beside the oval

For each major goal, write its trigger, success outcome and one important exception. The diagram stays a scope overview while the narrative provides enough detail to review the requirement. If the text becomes an ordered list of messages, it may be time for a separate sequence diagram.

Common questions

What does the use case diagram generator create?

It drafts a scope view showing external roles, their goals and a system boundary from your requirements.

Can another system be an actor?

Yes, if it is external to the chosen system boundary and interacts with it in a defined role.

Does a use case diagram show execution order?

No. Use a sequence diagram or process view to describe ordered interactions.

Do I need include and extend?

Only when those relationships clarify the model. A simple actor-to-goal diagram can be more useful for an initial scope discussion.

Sources and editorial notes

• UML Diagrams: Use case diagrams
• OMG: UML 2.5.1

Prepared by the AcaDraw product team on November 15, 2026. The reference illustration is original AI-generated artwork. It is a simplified explanatory model, not an experimental result, production specification or independently reviewed analysis.