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Unit 6: State Modelling
If there is a power cut, the washing machine will stop running and will go to the “Power Off” Notes
state. Then when the power is restored, the Running state is entered at the “History State”
symbol meaning that it should resume where it last left-off.
Figure 6.14: Use of History States
Source: http://www.ddegjust.ac.in/studymaterial/mca-5/mca-503.pdf
Concurrent Regions: A state may be divided into regions containing substates that exist and
execute concurrently.
Example: Figure 6.15 shows that within the state “Applying Brakes”, the front and rear
brakes will be operating simultaneously and independently. Notice the use of fork and join
pseudo-states, rather than choice and merge pseudo-states. These symbols are used to synchronize
the concurrent threads.
Figure 6.15: Concurrent Regions Example
Source: http://www.ddegjust.ac.in/studymaterial/mca-5/mca-503.pdf
A state machine diagram models the behavior of a single object, specifying the sequence of
events that an object goes through during its lifetime in response to events.
Example: The following state machine in Figure 6.16 shows the states that a door goes
through during its lifetime.
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