Masked prioritized synchronization for interaction and control of discreteevent systems

This paper extends the formalism of prioritized synchronous composition (PS C), proposed by Heymann for modeling interaction (and control) of discrete event systems, to permit system interaction with their environment via inte rface masks. This leads to the notion of masked prioritized synchronous com position (MPSC), which we formally define. MPSC can be used to model intera ction of systems at single as well as multiple interfaces. We show that MPS C can alternatively be computed by "unmasking" the PSC of "masked" systems, thereby establishing a link between MPSC and PSC, We next prove that MPSC is associative and thus suitable for modeling and analysis of supervisory c ontrol of discrete event systems. Finally, we use MPSC of a discrete event plant and a supervisor for controlling the plant behavior and show (constru ctively) that under the absence of "driven" events, controllability togethe r with normality of the given specification serve as conditions for the exi stence of a supervisor. This extends the results on supervisory control, wh ich permits control and observation masks to be associated with the plant o nly.