With
regard to the concrete execution, we often speak of a context object.
A state machine has no notation of its own. It is represented by the entire
state machine diagram. This means that the diagram frame forms the border of the
state machine. It is not possible to show a graphical connection between the state
machine and the pertaining class in the diagram ( Figure 3.56 ). However, the relationship
is explicitly present in the model.
A state machine forms a semantic capsule around states, transitions, and pseudostates.
This normally includes the execution rules. A state machine has a queue
for events that are consumed by states and transitions in the sequence in which
they occur. This means that they lead to state transitions, or to internal actions in
a state.
State machines are subject to the so-called run-to-completion semantics,
which says that the next event will be consumed only provided that all actions of
the previous event have been completed. One exception is the state behavior that
does not have to be completed before the next event can be processed.
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