Object-Oriented Implementation of the minimally restrictive liveness enforcing supervisory policy in a class of Petri nets
Sangeetha Chandrasekaran · 2013
Livelock avoidance is an essential requirement in Discrete-Event/Discrete-State (DEDS) systems. Every event of a live DEDS system can be executed at some instant in the future, irrespective of its past activities. When a DEDS system is in a livelock-state, some events will enter into a state of suspended animation for perpetuity, while others proceed with no impediment. This report is about the automatic synthesis of Liveness Enforcing Supervisory Policies (LESPs) for Petri net models of DEDS systems. Past research has shown that the existence of an LESP in DEDS systems modeled by a class of general Free-Choice Petri Nets (FCPNs) is decidable, and the minimally restrictive LESP is directly related to the presence of a right-closed set of states that are control invariant with respect to the system. A minimally restrictive LESP prevents the occurrence of events in a DEDS system only when it is absolutely necessary. This study describes an object-oriented implementation of the minimally restrictive supervisory policy for a class of Petri nets for which this policy is decidable. ii To my husband, for his patience To my mom and dad, for believing in me