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Chapter 29

Chapter 29. UML State Diagrams. Basics. Shows lifecycle of an object Event: Significant occurrence Example: Phone receiver taken off the hook Example: User moves to next level State: Condition of an object (or group of objects) at a moment in time Transition: A relationship between states

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Chapter 29

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  1. Chapter 29 UML State Diagrams

  2. Basics

  3. Shows lifecycle of an object • Event: Significant occurrence • Example: Phone receiver taken off the hook • Example: User moves to next level • State: Condition of an object (or group of objects) at a moment in time • Transition: A relationship between states • One transition: Object moves from one state to the other when a particular event occurs

  4. How to apply state machine diagrams? • Object state independent: • Response to a given event always the same • Object state dependent: • Based on state, object may respond differently to different events • Example: Ball hits gizmo • “state = quiet”  Response: Gizmo blinks • “state = sound on”  Response: Game makes sound • Use state machines for state-dependent objects with complex behavior

  5. When to use state machine diagrams? • Typically not useful in business information systems • More useful in “time varying systems” • Process control • Device control • Protocol handlers • Games • Telecommunications programs

  6. How are state machines used? • To model the behavior of a complex reactive machine (e.g. gizmo) in response to events • Example: Navigation between web pages in a site • Example: Event handling based on mode or conditions (e.g. Edit-Paste button active only if clipboard has stuff in it) • To model legal sequence of operations • Example: Protocol or language specifications

  7. More state diagram notation

  8. Nested (hierarchical states)

  9. UI Navigation Example

  10. NextGen State Machine Example

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