Implicit transition

Tutorial on SDL-88
Belina, Hogrefe (edits Reed)

In the language kernel, a process graph must contain a transition for all combinations of its states and the signals that the process can receive (these signals are called the complete valid input signal set). For some combinations the transition is empty and the state is not changed, that is the signal is consumed without any action. Such combinations need not be specified by the user of SDL in a process graph. For unspecified combinations the signal is consumed without any action