This domain implements the basic Petri Net model where Places and Transitions form a bipartite graph and enabled Transitions can fire randomly. It also allows Transitions to be replaced by any other Actors in Ptolemy. It implements two forms of Hierarchical and compositional Petri nets. The first form of hierarchical and compositional Petri net semantics comes from the fact that a Transition can contain a sub-Petri-net which is invisible to the director of the container of the Transition. The second form of hierarchical and compositional Petri net semantics comes from a new Actor called PetriNetActor which is a collection of Places and Transitions, and those Places and Transitions are visible to the director of the container of the PetriNetActor. The users can choose which form of models to use, and/or mix them together.
The basic Petri net is a directed, weighted, bipartite graph consisting of two kinds of nodes, called Places and Transitions, where arcs are either from a Place to a Transition or from a Transition to a Place. In graphical representation, Places are drawn as circles, Transitions as bars or boxes. Arcs are labeled with their weights (positive integers). Labels of unity weight are usually omitted. Multiple arcs can exist between a Place and a Transition. A marking assigns to each Place p an nonnegative integer k, we say that p is marked with k tokens. at the next iteration.