Beginners Guide to Model-Based Systems Engineering

12/18/2018

Returning to Behavior: Sequence Diagrams

• Emphasize interaction between collaborating parts of a system • Particularly powerful when used in understanding logical threads • Often become overloaded when representing complex logic • Includes lightweight representation of behavioral constructs

• Traditional systems approach included in SysML specification • Well understood (and often requested) by software engineers

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Key Semantics of Sequence Diagrams

• Blocks and lifelines • Interacting blocks (components) reflected at the top of the diagram • Lifeline shown as dashed line extending below block • Events • Execution instances of functions involved in the interaction • Represented as nodes on the lifeline

to which the function is allocated • Often unlabeled (emphasis on interaction between blocks)

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