Beginners Guide to Model-Based Systems Engineering

12/18/2018

Key Semantics of Use Case Diagrams: Use Case Relationships

• Drawn as ovals within the frame • Inclusion <> • Parent-child relationship between use cases • Child use case at the end of the arrow • Extension <> • Expansion of use case under specific conditions (extension point) • Extension use case at the tail of the arrow • Classification (unfilled arrowhead) • Generalization / specialization relationship between use cases • Specialized use case at the tail of the arrow

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Key Semantics of Use Case Diagrams: Other Relationships

• Actors and blocks

• Components involved in use case • Shown in outer ring

• Stick figure implies human • Block implies non-human

• Subject • System / component described by diagram • Shown as label at top of use case frame

Additional information available in Chapter 12 of A Practical Guide to SysML

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