Deadlock checking for one-place unbounded Petri nets based on modified reachability trees

A deadlock-checking approach for one-place unbounded Petri nets is presented based on modified reachability trees (MRTs). An MRT can provide some useful information that is lost in a finite reachability tree, owing to MRT's use of the expression a + bn(j) rather than symbol omega to represent the value of the components of a marking. The information is helpful In property analysis of unbounded Petri nets. For the dead lock-checking purpose, this correspondence paper classifies full conditional nodes in MRT into two types: true and fake ones. Then, an algorithm is proposed to determine whether a full conditional node is true or not. Finally, a necessary and sufficient condition of deadlocks is presented. Examples are given to illustrate the method.