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Use Case Arrows in UML

publish date: 2026/06/08 06:26:24.631407 UTC

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Formally, use case diagrams should use lines without arrowheads, yet arrows are often used informally. What do arrows indicate when used in a use case diagram?

That the use case is mandatory and must always be performed

The order in which use cases must be performed

The direction of data flow — from actor to system or vice versa

Which actor initiates the interaction

Correct Answer

Which actor initiates the interaction

Explanation

Formally, use case diagrams should use lines without arrows because in a use case messages pass in both directions. However, arrows are often used informally to indicate which actor initiates the interaction. For example, an arrow from the Medical Receptionist to the Transfer data ellipse informally shows that the receptionist initiates that transaction.

Reference

Software Engineering, Ian Sommerville, 9th edition

Quizzes you can take where this question appears

Interaction Models