A SAT-Based Approach for the Construction of Reusable Control System Components

Modeling the Supervisory Control Theory with Alloy

“…Without exploiting this hierarchical framework, it would have been impossible to achieve such a level of scalability with Alloy. In this paper, we provide, among other things, solutions for some open issues raised in [5].…”

“…Based on these two studies [4,5], we drew the following conclusions. Firstly, properties to be satisfied are often expressed on languages, more often, infinite sets of words over an event alphabet.…”

“…When this is not the case, a manual proof is necessary to show that the new formulation is correct w.r.t. the given property (e.g., the observer property for which such a proof, missing in [5], is given in Section 3.4). Secondly, attempts to automatically generate supervisors were unsatisfactory because such processing includes the computation of a supremal element and there is no guarantee that the SAT-solver will find the optimal solution unless it is called inside an iterative procedure that checks if optimality has been reached (such a procedure is only mentioned in [5], but now described in Section 4).…”

“…the given property (e.g., the observer property for which such a proof, missing in [5], is given in Section 3.4). Secondly, attempts to automatically generate supervisors were unsatisfactory because such processing includes the computation of a supremal element and there is no guarantee that the SAT-solver will find the optimal solution unless it is called inside an iterative procedure that checks if optimality has been reached (such a procedure is only mentioned in [5], but now described in Section 4). Thirdly, sometimes an iterative process has to take place when human intervention is required in order to obtain, for instance, a useful interface for a software component while satisfying specific properties prescribed by the theory.…”

“…They also proposed a synthesis process via an iterative specification refinement without giving any concrete implementation. To avoid complex encoding schemata, Côté et al [5] used Alloy to verify several properties defined in the hierarchical control architecture framework of SCT [17] in order to generate observers and supervisors associated with small reusable components. Indeed, among 44 components of a modular production system, 75 % of those components have been successfully checked by the Alloy analyzer, the other 25 % could not because their state space was too large.…”