petri-net

Petri net boundedness


I want to ask about petri net(PN) boundedness. When I have a state s1 = (2 0 0) then i find state s2 = (2 0 1) so since s1 < s2 can I declare PN as NOT bounded ? Because when I have this PN: PN

PN is bounded but u can find there (2 0 0) < (2 0 1). So my question is. Am I wrong about boundedness of petri net or is something wrong with PT on the picture ?


Solution

  • This net is bounded. You can check this by building its reachability graph.

    Initially only one transition t1 is enabled. Therefore s1=(2 0 0) has only one successor state s2 = (1 1 0). Here is the full reachability graph

    reachability graph of the Petri net

    Also observe that there is no transition that has more outgoing arcs than incoming arcs, therefore the number of tokens in the net cannot increase. This is called an invariant. From this observation you can derive that the state (2 0 1) can never be reached from (2 0 0).