On supervisor reduction in discrete-event systems

A supervisory controller (supervisor) S for a discrete-event system can be modelled on a recognizer R for the language corresponding to the supervisory task to be accomplished. It is shown that simpler ‘reduced’ supervisors can be constructed by the use of covers of the state set of R; and that any mildly restricted supervisor is a reduction of R in this sense. The reduction procedure is time-exponential with respect to the size of the state set of R.