Supervisory Control for Modal Specifications of Services

Abstract

In the service oriented architecture framework, a modal specification, as defined by Larsen in [6], formalises how a service should interact with its environment. More precisely, a modal specification determines the events that the server may or must allow at each stage in an interactive session. Therefore, techniques to enforce a modal specification on a system would be useful for practical applications. In this paper, we investigate the adaptation of the supervisory control theory of Ramadge and Wonham to enforce a modal specification (with final states marking the ends of the sessions) on a system modelled by a finite LTS. We prove that there exists at most one most permissive solution to this control problem. We also prove that this solution is regular and we present an algorithm for the effective computation of the corresponding controller.Key-words: discrete event systens, supervisory control, modal specifications, services, partial observation. Synthèse de contrôleurs pour des services décrits par des spécifications modalesRésumé : Dans le cadre d'une architecture orientée services, une spécification modale décrit les interactions possibles ou nécessaires entre un service et l'environnement utilisateur de ce service. Plus précisément, une spécification modale détermine les actions que le serveur peut ou doit permettreà son utilisateurà chaqueétape d'une session interactive. Développer des techniques de supervision permettant de forcer la conformité d'un systèmeà une spécification de service s'avère utile. Dans cet article, nous cherchonsà adapter les techniques de synthèse de contrôleurs afin de forcer la conformité de systèmes finisà des spécifications modales (avec desétats marquant les fins de sessions). Nous montrons que ce problème de contrôle a une plus grande solution. Nous montronségalement que cette solution est régulière et donnons un algorithme pour la calculer.

On the specification of modal systems: A comparison of three frameworks

“…In particular, results on the supervisory control (in the sense of Ramadge and Wonham [21]) of systems whose specification is given in that formalism have been presented in, e.g., [8,12].…”

Ensuring Reachability by Design

“…Marked modal specifications look similar to the modal specifications with marked states introduced in [6]. However, these two formalisms are very different because the satisfaction relation in [6] admits implementations having final states corresponding to a state of the specification that is not final.…”

“…However, these two formalisms are very different because the satisfaction relation in [6] admits implementations having final states corresponding to a state of the specification that is not final. This is appropriate in the context of supervisory control synthesis.…”

“…Following [6], we enrich modal specifications [18,16,3] with marked states in order to model states to be reached. For instance, if a designer specifies a service, this enables to represent session terminations.…”

“…The role of these operators in a design flow will be motivated later in the paper. As reachability properties cannot be expressed, in general, with modal specifications, we first consider in this paper modal specifications enriched with marked states, in the same fashion as it is done in [6]. We show that, in this framework, we can develop a theory ensuring reachability properties by design.…”