Petri net: различия между версиями

A ''' Petri net''' is a finite  directed graph with two types of nodes,

referred to as '''places''' and '''transitions'''. It is a bipartite graph: every arc

goes either from a place to a transition or from a transition to a place.

Consider a transition <math>t</math>. Every place <math>p</math> (respectively, <math>q</math>) such that there is an arc from <math>t</math> to <math>p</math>

(respectively, from <math>q</math> to <math>t</math>) is called an '''input'''

The same place can be both an input and an output place of <math>t</math>.

We now define the '''operation''' (or '''execution''') of a Petri net.

A transition is '''enabled''' (at a marking) iff all its input places have at least one token.

adding one token to each of its output places.

A transition is not enabled if there are not sufficiently many tokens in each

of its input places.