Incremental model evolution and reusability of supervisors for discrete event systems

System evolution, such as addition or replacement of a component, recon"guration upon a diagnosed failure, or process changes leading to new requirements on the system behavior, may often invalidate the existing supervisors for a discrete event system. While redesigning these supervisors for the evolved system is always an option, it is often an expensive and time-consuming task. A more practical approach is to attempt, if possible, to reuse these supervisors for enforcing the original set of speci"cations. The objectives of this work are to: (i) study conditions on the evolution of the system model under which it is possible to reuse the existing supervisors, and (ii) propose a systematic method for this reuse of the supervisors, based on the automatic synthesis of input and output `interfacesa, when the conditions identi"ed in (i) hold. ( 1999 Elsevier Science Ltd. All rights reserved.