MBSE with CORE 100821

Completing the Use Cases (a diagram is not enough) A common error is stopping at the use case diagram Each use case must have • Description • Pre-conditions – a description of the conditions before the use case begins • Post-conditions – a description of the conditions after the use case ends A use case may optionally have (often specified via formal behavior instead) • Primary flow – a narrative of the standard behavioral flow to move from pre-condition to post-condition • Alternate flow – a narrative of the off-nominal cases to move from pre-condition to post-condition under

293

Key Semantics of Use Case Diagrams

• 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 • Specialization inherits characteristics of its parent and then adds additional characteristics

294

MBSE with CORE