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?–  The do behavior is executed while the state is active.
In Figure 3.58 , you can see internal behavior in the state machine of a railroad
crossing. This example utilizes the fact that the state behavior is interruptible. For
example, the barriers are closed in the state block . The state behavior close() is
interrupted by the event endPosition(down) . The entry behavior and the exit
behavior are not interruptible.
An important UML extension versus the classic Finite State Machine ( FSM )
is the possibility to decompose states into smaller units. This allows us to fi rst
describe states on a general level and then further detailing them.
Figure 3.59 shows the state Day after further detailing. It is a so-called composite
state, containing a region with states and transitions. We can recognize this
by the ??? spectacles ??? symbol in the lower right corner of the state in the upper diagram.
The detailing itself is not shown here; it is shown in the bottom diagram.
stm Notation for state
State
event [condition]/behavior
State
State
FIGURE 3-57
Notation for state.


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