Аннотация:Petri nets are a modeling mechanism that allows you to describe both the possible states of a system and its possible actions. A Petri net consists of four elements: P - a set of positions, T - a set of transitions, I - an input function,and O - an output function. Positions describe the state, and transitions describe the actions taking place in the network. The network structure is a quartet of elements C = (P, T, I, O), where P and T are finite sets of positions and transitions.The input function I maps a transition t to a set of input positions, I(tj ), and the output function O maps a transition t to a set of output positions, O(tj ), i.e., a transition can have both input and output positions, including repetitions.