Incremental model evolution and reusability of supervisors for discrete event systems (Q1962005)

The discrete event model of a dynamic system that is used for supervisory control purposes may often need to be altered when the system is modified or reconfigured. Such evolution of system models could necessitate complete redesign of supervisory controllers. The redesign involves building the new models and requires considerable computational efforts. Here, the authors present an approach to reuse the existing supervisor by additions to it new parts. They propose two types of model evolution: vertical growth (when transitions of the original system model are refined, i.e. the system behavior is modelled with more details using additional events) and horizontal growth (when a new part is added to the original system model). For vertical growth, the authors have found a set of sufficient conditions on the model evolution under which the original supervisors can always be reused. In the case of horizontal growth, the authors have found a closed-form representation of evolved system behavior under sole control of the reused supervisors. In the conclusion, some criteria of expediency of supervisor reusing are discussed.