Modeling Constraint-based Processes: a Supervisory Control Theory Application

Eduardo Alves Portela Santos, Agnelo Denis Vieira, Sauro Schaidt, Eduardo de Freitas Rocha Loures

Constraint-based processes require a set of rules that limit their behavior to certain boundaries. In these processes, the control flow is defined implicitly as a set of constraints or rules, and all possibilities that do not violate any of the given constraints are allowed to be executed. The present paper proposes a new approach to deal with constraint-based processes. The proposed approach is based on Supervisory Control Theory, a formal foundation for building controllers for discrete-event systems. The controller proposed in this paper monitors and restricts execution sequences of activities such that constraints are always obeyed. We demonstrate that our approach may be used as a declarative language for constraint-based processes. In order to provide support for users of such processes and to facilitate the using of our control approach, we offer a set of constraints modeled by automata. This set encompasses the constraints frequently needed in workflow system.