Characterization and computation of classes of co-observable languages for decentralized control of discrete event systems

We present fixed-point based characterization of several classes of co-observable languages that are of interest in context of decentralized supervisory control of discrete event systems. Using the fixed-point based characterization, we are able to obtain iterative methods for computing superlanguages and sublanguages belonging to the various classes of co-observable languages. We also study the closure properties under union and intersection of the classes of co-observable languages, and also verify if the fixed-point operators preserve either the property of relative closure (also called L_m(G)-closure) or that of prefix closure.