Transitions of a model are triggered by events, and they react to them. They may or may not change the state of the model. They are graphically shown as arcs or arrow lines.
A transition has several properties:
The guard and output of a transition are optional and may be omitted from the graphical representation of the model for better conciseness. It is not allowed to create a transition without an event name. For a transition whose triggering does not depend on any event, i.e., the transition is triggered whenever the source state is entered (and with its guard evaluated to true, if any), the model designer must explicitly specify as the event name. Because DCharts is a real-time formalism, does not mean to trigger the transition at no time but rather as soon as possible (after all the currently queued events have been handled).
Figure 4.7 shows a model with three transitions. (Note that the arc from a black dot to a state is not a transition but part of the notation of a default state.) The transition from B to A reacts to event e if and only if condition i==1 is satisfied. As a side effect of the triggering of this transition, action [DUMP("t1 fired")]4.1 is executed.
Figure 4.8 shows the graphical representation of the same model in AToM.