1. UML State Diagrams (Ch. 29)

2. State Diagrams State diagrams:
Provides another dynamic view of aspects of system
Expresses:
Events
States
Behavior of an object in reaction to an event
Shows behavior of an object

3. Fig. 29.1

4. State Diagrams Terminology:
Event – a significant occurrence (instantaneous, has no duration)
State – a condition of an object, time between events (has duration)
Transition – object moves from one state to another, triggered by an event
Notation for each

5. State Diagrams
Guideline: Consider state diagrams for state-dependent objects with complex behavior
Guideline:
Business information systems typically have few state-dependent classes/objects
Process control, device control, protocol handlers, communications systems typically have many state-dependent objects
See p. 488 for examples

6. State Diagrams Notations:
Action – an event may cause an action to fire
Conditional guard – a transition may be guarded by a boolean test, the transition fires only if event occurs at a point where test is true

7. State Diagrams Nested states a state can contain substates
substates inherit transitions of enclosing state

8. Applying state diagram to web page navigation
State Diagrams
Applying state diagram to web page navigation

9. State Diagrams Example from POS system:
State diagram shows legal sequencing of use case operations . . .

10. Fig. 29.5