 System Sequence Diagrams Sheridan SYST Engineering Quality Systems 11

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 System sequence diagram (SSD) o Describes flow of information o Identifies interaction between actors and system o Message oriented Sheridan SYST Engineering Quality Systems 3

 Actor “interacts” with the system via input/output  SSDs use object notation o Box (rectangle) refers to individual object o Name of the object underlined o Messages sent/received by objects, not classes  Lifeline o Extension of object or actor for duration of the SSD o Indicates sequence of the messages sent/received Sheridan SYST Engineering Quality Systems 4

Sample System Sequence Diagram Sheridan SYST Engineering Quality Systems 5

 Message syntax can take several forms o Depends on send/return direction  Message semantics: actions (like commands) invoked on destination object Sheridan SYST Engineering Quality Systems 6

 Begin with detailed description of use case o Fully developed form o Activity diagrams  (4) step process for turning activity diagram into SSD o [1] Identify the input messages o [2] Describe messages from external actor to system o [3] Identify/apply special conditions to input messages o [4] Identify and add the output return messages Sheridan SYST Engineering Quality Systems 7

A Simplified Diagram of the Telephone Order Scenario Sheridan SYST Engineering Quality Systems 8

An SSD of the Simplified Telephone Order Scenario for the Create New Order Use Case Sheridan SYST Engineering Quality Systems 9

 Names of messages reflect services performed  Important principle for identifying data parameters o Base the list on the class diagram o Attributes from the classes listed as parameters  Iteratively define input/output parameters around workflows  Objective: discovery and understanding Sheridan SYST Engineering Quality Systems 10

 Sequence diagrams are used to show flow of control  When preparing program code, a sequence diagram helps to capture the dynamic aspects of the system by implementing the operations, messages, and the sequencing of those messages in the programming language Sheridan SYST Engineering Quality Systems 11

 Use Case Diagram Use Cases  Class Diagram  State Charts  Sequence Diagram Sheridan SYST Engineering Quality Systems 12

Generates Is sold at Sheridan SYST Engineering Quality Systems 13

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Sheridan SYST Engineering Quality Systems 15 Reserve Car Customer requests a rental Customer Service Representative (CSR) enters request to vehicle rental system System retrieves and displays available vehicles CSR confirms vehicle request including date, duration, and rental pricing. CSR enters reservation details. System creates new reservation. System generates confirmation no. CSR informs Customer