SENG 403 SENG 403 – Winter 2012

 Brief introduction to SSD  Example (A sales systems (Cashier))  Example (Monopoly game) SENG 403 – Winter 2012

 A system sequence diagram (SSD):  is a fast and easily created artifact.  illustrates input and output events related to the systems. SENG 403 – Winter 2012

 A fast review of the notions and rules in UML sequence diagrams SENG 403 – Winter 2012

 The sender waits until the receiver has finished processing the message, only then does the caller continue (i.e. a blocking call).  Most method calls in object-oriented programming languages are synchronous.  A closed and filled arrowhead signifies that the message is sent synchronously. SENG 403 – Winter 2012

 If you want to show that the receiver has finished processing the message and returns control to the sender, draw a dashed arrow from receiver to sender. ▪ Optionally, a value that the receiver returns to the sender can be placed near the return arrow SENG 403 – Winter 2012

 A message of which the caller is not shown.  Either ▪ the sender is not known, ▪ or that it is not important who the sender was.  Originates from a filled circle SENG 403 – Winter 2012

 The sender does not wait for the receiver to finish processing the message  An open arrowhead is used to indicate that a message is sent asynchrously. SENG 403 – Winter 2012

 An object sends to itself SENG 403 – Winter 2012

 The time it takes to arrive at the receiver is negligible.  Drawn as a horizontal arrow. SENG 403 – Winter 2012

 Sometimes it takes a considerable amount of time to reach the receiver.  E.g. across a network.  Such a non-instantaneous message is drawn as a slanted arrow. SENG 403 – Winter 2012

 Prefixed with an asterisk.  The message is sent repeatedly.  A guard indicates the condition that determines whether or not the message should be sent (again). SENG 403 – Winter 2012

 Sending the same message to different elements in a collection.  The receiver of the repeated message is a multiobject. SENG 403 – Winter 2012

 Multiple messages sent in the same iteration  a 'loop' combined fragment can be used. SENG 403 – Winter 2012

 The message is only sent if a certain condition is met.  The condition is between brackets. SENG 403 – Winter 2012

 Several messages conditionally sent under the same guard (condition). ▪ Use an 'opt' combined fragment.  The combined fragment is shown as a large rectangle with an 'opt' operator plus a guard ▪ contains all the conditional messages under that guard SENG 403 – Winter 2012

 Alternative interactions ▪ use an 'alt' combined fragment. SENG 403 – Winter 2012

 Success scenario of a cash- only Process Sale scenario.  The cashier generates makeNewSale, enterItem, endSale, and makePayment system events. SENG 403 – Winter 2012

 In the current iteration (for this sales system) we are considering the following scenarios and system operations:  makeNewSale  enterItem  endSale  makePayment SENG 403 – Winter 2012

 “enterItem” is better than “scan” (that is, laser scan) because it captures the intent of the operation while remaining abstract and noncommittal with respect to design choices about what interface is used to capture the system event.  It could by via laser scanner, keyboard, voice input, or anything. SENG 403 – Winter 2012

1. Initialization 2. Play game SENG 403 – Winter 2012

 Website (tool): ▪ Trace modeller (UML Sequence Diagram Editor) ▪ A gallery of UML sequence diagrams:   Book:  Craig Larman, Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and the Unified Process (3nd Edition), Prentice Hall PTR.  Chapters 10, 15 and 18  Video:  UML Sequence diagram basics review: ▪  Online article: ▪ Donald Bell, IBM Corporation, UML Basics: The sequence diagram. SENG 403 – Winter 2012