Controlled Petri nets and general legal sets

Proves a reduction theorem for the supervisory control of general controlled Petri nets, with general legal sets. The reduction theorem shows that in order to design a maximally permissive control law guaranteeing that the marking always remains in the legal set, it is sufficient to consider a sub-Petri net of the full model. This extends the design algorithms which were previously known for special classes of Petri nets, and for special classes of legal sets. The reduction theorem allows us to prove a useful property of maximally permissive control laws, and to limit the number of events which must be observed