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BTS430 Systems Analysis and Design using UML. System Sequence Diagrams. AGENDA. Use Case Specifications returned Introduction of System Sequence Diagrams Exercises. System Sequence Diagrams.
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BTS430 Systems Analysis and Design using UML System Sequence Diagrams
AGENDA • Use Case Specifications returned • Introduction of System Sequence Diagrams • Exercises
System Sequence Diagrams • A system sequence diagram …. Illustrates input and output events related to the system under discussion. • Larman, APPLYING UML AND PATTERNS, p. 173
System Sequence Diagrams • The use case text and its implied system events are input to a SSD (system sequence diagram). • Larman, APPLYING UML AND PATTERNS, p. 174
System Sequence Diagrams • Use cases describe how external actors interact with the software system… • An actor generates system events to a system, requesting some system operation to handle the event. • The use case text implies the event…the SSD makes it concrete and explicit. • Larman, APPLYING UML AND PATTERNS, p. 176
System Sequence Diagrams • A system sequence diagram is a picture that shows, for one particular scenario of a usecase, the events that external actors generate, their order and the inter-system events. • All systems are treated as a black box. • Larman, APPLYING UML AND PATTERNS, p. 176
Why Draw System Sequence Diagrams? • The external input events—the system events are an important part of analyzing system behavior. • System behavior is a description of what a system does, without explaining how it does it. • Larman, APPLYING UML AND PATTERNS, p. 173
System Sequence Diagrams • System events should be expressed at the abstract level of intention rather than in terms of the physical input device. • Larman, APPLYING UML AND PATTERNS, p. 178
How Many System Sequence Diagrams? • One for each frequent scenario • One for each complex scenario • Larman, APPLYING UML AND PATTERNS, p. 176