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System sequence diagram

System sequence diagram. M Taimoor Khan taimoorkhan@ciit-attock.edu.pk. System sequence diagram. SSD is a picture that shows for one particular scenario of a use case, the events that external actors generate which trigger some inter-system events

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System sequence diagram

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  1. System sequence diagram M Taimoor Khan taimoorkhan@ciit-attock.edu.pk

  2. System sequence diagram • SSD is a picture that shows for one particular scenario of a use case, the events that external actors generate which trigger some inter-system events • This diagram treats the system as black box and only emphasis on events that cross the system boundary from actor to system • It illustrates inputs and outputs to the system

  3. Motivation behind SSD • The motivation behind SSD is to design a pattern for handling external system requests and producing proper response • Events may be external (triggered by human or computer), time events or fault / exception events • It is useful to investigate and define system’s behavior as “black box” before proceeding with the detailed design • It shows events from one scenario of a use-case diagram and operations performed by system in response

  4. Partial System sequence diagram

  5. System events • System events: External input to system generated by actor • System operation: Methods invoked in response to system events • System events may have arguments • enterItem( UPC, quantity ) • raise( money )

  6. System sequence diagram

  7. Naming system events and operations

  8. Difference with sequence diagram • Sequence diagram shows the internal operations of the system triggered by events. • It ignores the external events source • Operations are drawn between different objects of the system • The flow of messaging is maintained

  9. book:Book :BookCopy borrow(book) ok = mayBorrow() setTaken(member) A Sequence Diagram member:LibraryMember [ok] borrow(member) Sequence Diagrams

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