1. UML State Diagrams

2. State Diagrams
State Diagrams are used to model the behavior of an individual object across its entire lifetime (i.e., across all use cases that it participates in)

3. State Diagrams A State Diagram shows
The different states that an object can be in
The events that cause the object to change states
The actions performed by the object when it changes state
Basically just a finite state machine with some fancy features

4. State Diagrams
Any class may have a State Diagram that describes the behavior of its instances
Only create State Diagrams for classes that exhibit interesting "stateful" behavior
Object's current behavior depends on its past in non-trivial ways
State Diagrams contain:
States
Transitions

5. States
A state is a situation during the life of an object during which it satisfies some condition, performs some activity, or waits for some event
Example: Thermostat

6. Transitions
A transition is a relationship between two states indicating that an object in the first state will perform certain actions and enter the second state when a specified event occurs and specified conditions are satisfied

7. Transitions Event Guard Action Message received or passage of time
Boolean expression that determines whether transition is enabled
Action
Executable, atomic computation performed when transition is taken
Send message, create object, etc.

8. Transitions
Example: Thermostat

9. Transitions
Example: AlarmClock

10. Initial / Final states
Example: Thermostat

11. Advanced Features
State Diagrams have many advanced features that are not discussed here