Contracts for modular discrete controller synthesis

Abstract

International audienceWe describe the extension of a reactive programming language with a behavioral contract construct. It is dedicated to the programming of reactive control of applications in embedded systems, and involves principles of the supervisory control of discrete event systems. Our contribution is in a language approach where modular discrete controller synthesis (DCS) is integrated, and it is concretized in the encapsulation of DCS into a compilation process. From transition system specifications of possible behaviors, DCS automatically produces controllers that make the controlled system satisfy the property given as objective. Our language features and compiling technique provide correctness-by-construction in that sense, and enhance reliability and verifiability. Our application domain is adaptive and reconfigurable systems: closed-loop adaptation mechanisms enable flexible execution of functionalities w.r.t. changing resource and environment conditions. Our language can serve programming such adaption controllers. This paper particularly describes the compilation of the language. We present a method for the modular application of discrete controller synthesis on synchronous programs, and its integration in the BZR language. We consider structured programs, as a composition of nodes, and first apply DCS on particular nodes of the program, in order to reduce the complexity of the controller computation; then, we allow the abstraction of parts of the program for this computation; and finally, we show how to recompose the different controllers computed from different abstractions for their correct co-execution with the initial program. Our work is illustrated with examples, and we present quantitative results about its implementation

Integrating discrete controller synthesis into a reactive programming language compiler

“…Another modular contract example has been developed, with simplified behaviors involving only delayable tasks, but showing the use of modularity, and also the methodology: we first constructed a contract node for n such tasks, and then built a 2n tasks node, with a first contract that revealed itself being not controllable, and then refinements of the problem leading to a solution. On this example performance evaluation showed a drastically improved scalability of the approach [12].…”

“…A companion paper describes how compilation works with modular DCS computations [12], whereas this paper defines the programming language semantics in a denotational way. Previous work, preceding these papers, involved some separate and partial aspects of the problem, testing the idea in the framework of a more modest specialized language and elaborating on the articulation between reactive programs and DCS [33,2].…”

“…Hence, it exists causality problems between these variables and the variables of the upper level. See [12] for more details.…”

“…On the examples given on table 1, all execution times for one step of the controlled system (thus including execution of the controller itself) are of the order of few µseconds. Moreover, we have some more thorough experiments regarding performance and size of systems that can be managed [12], which show that scalability is greatly enhanced by modular synthesis.…”

A domain-specific language for the control of self-adaptive component-based architecture

“…For that purpose, we formally define the semantics of Ctrl-F behavioural programs by the translation to a FSA model [12]. More precisely, we provide full translation from Ctrl-F to the reactive language Heptagon/BZR [13], which allows the compilation towards formal tools and thereby benefit from exploration by both DCS and verification.…”