Petri-Net and Augmented-Petri-Net

A simple graph representation of a Petri-net is illustrated in Figure 1. The graph contains two types of nodes: circles (called places ) and bars (called transitions ). These nodes are connected by directed arcs from places to transitions and from transitions to places. If an arc is directed from node i to node j (either from a place to a transition or a transition to a place), then i is an input to j, and j is an output of i. In Figure 1, for example, place p1 is an input to transition t2, while places p2 and p3 are outputs of transition t2.


Figure 1. A simple graph representation of the Petri net.