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Chapter 10

Chapter 10. System sequence diagrams. A System Sequence Diagram. System Sequence Diagrams. Simple diagrams that illustrate input and output events to the system Serve as input to operation contracts object design to be covered later SSDs are ONE particular use of UML Sequence diagrams

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Chapter 10

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  1. Chapter 10 System sequence diagrams

  2. A System Sequence Diagram

  3. System Sequence Diagrams • Simple diagrams that illustrate input and output events to the system • Serve as input to • operation contracts • object design to be covered later • SSDs are ONE particular use of UML Sequence diagrams • System treated as black box • Interactions with external actors detailed • Guideline: • One SSD per “main success scenario” of a use case • Frequent or complex alternative scenarios

  4. SSD for main success scenario of the ProcessSale Use Case

  5. Why draw an SSD? • Isn’t all of this already in the use case narrative? • Input and output events along with their arguments (associated information) are made explicit • Put detailed explanations of certain event names, arguments in the Glossary

  6. Naming Events

  7. Monopoly SSD example

  8. Chapter 11 Operation Contracts

  9. Operation contracts: Detailed description of changes to objects in domain model in response to events • Use pre- and post- conditions • What is the difference from a use-case narrative? • There the pre- and post- conditions are described for the entire use case • Here pre- and post- conditions are described per system event

  10. Example contract

  11. Sections of a contract

  12. Postconditions • For important, non-trivial system events, describe changes in the state of the objects in the domain model • Changes include • instances created • associations (UML links) formed or broken • attributes changed • May result in updates to the domain model • Additions of new attributes and associations

  13. Example contract

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