Page 72 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Object Oriented Analysis and Design

Notes
Figure 6.3: Final State

Source: http://www.ddegjust.ac.in/studymaterial/mca-5/mca-503.pdf
Transitions: Transitions from one state to the next are denoted by lines with arrowheads. A
transition may have a trigger, a guard and an effect, as shown in Figure 6.4 below.

Figure 6.4: Transitions

Source: http://www.ddegjust.ac.in/studymaterial/mca-5/mca-503.pdf
“Trigger” is the cause of the transition, which could be a signal, an event, a change in some
condition, or the passage of time.

Notes “Guard” is a condition which must be true in order for the trigger to cause the
transition. “Effect” is an action which will be invoked directly on the object that owns the
state machine as a result of the transition.

State Actions: In the transition example above, an effect was associated with the transition. If the
target state had many transitions arriving at it, and each transition had the same effect associated
with it, it would be better to associate the effect with the target state rather than the transitions.
This can be done by defining an entry action for the state.

Example: The diagram in Figure 6.5 below shows a state with an entry action and an exit
action

Figure 6.5: State with an Entry Action and an Exit Action

Source: http://www.ddegjust.ac.in/studymaterial/mca-5/mca-503.pdf
It is also possible to define actions that occur on events, or actions that always occur.

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