Masked prioritized synchronization for interaction & control of discrete event systems

This paper extends the formalism of prioritized synchronous composition (PSC), proposed by Heymann for modeling interaction (and control) of discrete event systems, to permit system interaction with their environment via interface masks. This leads to the notion of masked prioritized synchronous composition (MPSC), which we formally define. We show that MPSC can alternatively be computed by "unmasking" the PSC of "masked" systems, thereby establishing a link between MPSC and PSC. We next show that MPSC is associative and thus suitable for modeling and analysis of supervisory control of discrete event systems. Finally, we use MPSC of a discrete event plant and a supervisor for controlling the plant behavior and show (constructively) that controllability together with normality of the given specification serve as conditions for the existence of a supervisor.