Reduction of the supervisory control problem for Petri nets

The authors prove a reduction theorem for the supervisory control problem for general Petri nets with general legal sets. To design control laws guaranteeing that the marking stays within the legal set, it suffices to consider a sub-Petri net of the full model. This extends existing design algorithms, allows to prove an important property of maximally permissive control laws and limits the number of events which need to be observed.