What is a State?
(Tutorial Page 13)
  • State is an abstraction of the attribute values and links of an object
    1. A Car's power affects Car speed
    2. Engine speed is an attributes that affects Car speed
    3. A gear that the Car is in affects the behavior (or constrains) the Car speed.
    4. Set of values are grouped together into a set which affect the behavior of the object
    5. The combination of power, engine speed and gear are grouped into each state

  • State ignores attributes which are irrelevant to the behavior of an object.
  • When looking at the behavior of the Car, its color is irrelevant to the Car state.
  • A state specifies the response of an object to an input event
    1. Depress Accelerator might be events that affect the state of the car.
    2. Depress Accelerator is an event, the speed of the car is its state.

  • A state corresponds to an interval (a pause) between two events
    1. The car is in a state of normal speed (normal being 70MPH), an event Brake or
    2. Accelerate, affects the resultant state.

  • A state has duration, it takes time compared to an event
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