Java Petri Net Sim
JPetri is a Java program that allows the simulation of colored Petri Nets.
A Petri net is a directed bipartite graph, in which the nodes represent transitions (i.e. discrete events that may occur, signified by bars), places (i.e. conditions, signified by circles), and directed arcs (that describe which places are pre- and/or postconditions for which transitions, signified by arrows). Petri nets were invented by Carl Adam Petri for the purpose of describing chemical processes.