Test on Zero in Petri Nets

In this note we discuss some aspects of nets (i. e. Petri-nets, place/transition nets, P/T-nets) augmented by inhibitor arcs. An inhibitor arc connects a transition t with a place p. For such a transition the firing rule is modified as follows. Transition t fires under the usual conventions, when p is empty, but is inhibited from firing, if p contains at least one token. This behaviour can be represented by ordinary nets only in those cases, where p is a bounded place. Nets, where inhibitor arcs are allowed, will be called inhibitor nets or I-nets in this paper.