Abstract: A marking M is said to be an empty marking in a Petri net ∑= （S, T; F, M） if M（s） = 0 for every s∈S[1]. An empty marking may be an initial marking of a net system, or a reacheable marking for a net system of which the initial marking is not empty[1]. Repr

Key words: Petri net, Empty making, Liveness, Reachability