Petri-Net and Augmented-Petri-Net
A Petri-net is an abstract, formal model of information flow.
The properties, concepts, and techniques of Petri-nets are
developed in a search for natural, simple and powerful methods
for describing and analyzing the flow of information and control
in systems, particularly systems that may exhibit asynchronous and
concurrent activities. The major use of Petri-nets has been the
modelling of systems of events in which it is possible for
some events to occur concurrently but there are constraints on the
concurrence, precedence or frequency of these occurrences.