Esterel Studio Research Articles

Specification and verification of time requirements with CCSL and Esterel

The UML Profile for Modeling and Analysis of Real-Time and Embedded (MARTE) systems has recently been adopted by the OMG. Its Time Model extends the informal and simplistic Simple Time package proposed by UML2 and offers a broad range of capabilities required to model real-time systems including discrete/dense and chronometric/logical time. MARTE OMG specification introduces a Time Structure inspired by Time models of the concurrency theory and proposes a new clock constraint specification language (CCSL) to specify, within the context of UML, logical and chronometric time constraints. This paper introduces the formal semantics of a fundamental subset of CCSL clock constraints and proposes a process to use CCSL both as a high-level specification language for UML models and as a golden model to verify the conformance of implementations with the specification. A digital filtering video application is used as a running example to support the discussion. The application is first formally specified with CCSL and the specification is refined based on feedback from our CCSL-dedicated simulator. In a second phase, an Esterel program of the application is considered. This program is instrumented with observers derived from the CCSL specification. Esterel Studio formal verification facilities are then used to check the conformity of the Esterel implementation with the CCSL specification. A specific library of Esterel observers has been built for this purpose.

Verification and validation of a SSM model dedicated to mode handling of flexible manufacturing systems

This paper focuses on verification and validation of a model dedicated to mode handling of flexible manufacturing systems (FMSs). This model is specified using the synchronous formalism safe state machines (SSMs). The rigorous semantics that characterize such formalism enable to provide formal verification mechanisms ensuring determinism and dependability. A structured framework for verification and validation of the model dedicated to mode handling is proposed. The main properties being verified within this framework and the corresponding verification methods are presented. The approach is illustrated using an example of a manufacturing production cell. The formal analysis tools integrated into the development environment Esterel Studio are used within the design process.

Embedded Systems Programming: Accessing Databases from Esterel

AbstractA current limitation in embedded controller design and programming is the lack of database support in development tools such as Esterel Studio. This article proposes a way of integrating databases and Esterel by providing two application programming interfaces (APIs) which enable the use of relational databases inside Esterel programs. As databases and Esterel programs are often executed on different machines, result sets returned as responses to database queries may be processed either locally and according to Esterel's synchrony hypothesis, or remotely along several of Esterel's execution cycles. These different scenarios are reflected in the design and usage rules of the two APIs presented in this article, which rely on Esterel's facilities for extending the language by external data types, external functions, and procedures, as well as tasks. The APIs' utility is demonstrated by means of a case study modelling an automated warehouse storage system, which is constructed using Lego Mindstorms robotics kits. The robot's controller is programmed in Esterel in a way that takes dynamic ordering information and the warehouse's floor layout into account, both of which are stored in a MySQL database.

Towards a Model Theory for Esterel

Esterel is a synchronous language for reactive-systems design and builds the core of the commercial tool Esterel Studio. This paper shows how the constructive semantics of a combinational fragment of Esterel, as presented by Berry, can be derived in a model-theoretic fashion, thus complementing the existing behavioral, operational, and circuit-based approaches to Esterel semantics. Technically, Esterel programs are read as formulas in propositional intuitionistic logic, which are interpreted over simple linear Kripke structures, referred to as Gödel valuations. Esterel reactions are then characterized as specific Gödel valuations, called response models, and it is shown that the approach is compositional in the structure of Esterel programs.The obtained results are an important step towards explaining the logic behind Esterel semantics. In addition, the intuitionistic setting advocated in this paper nicely links to Pnueli and Shalev's semantics of Harel's Statecharts, another synchronous language for reactive-systems design. This offers interesting insights into the similarities of and the differences between Esterel and Statecharts semantics.

Design of an Automatic Teller Machine with Esterel Studio

Abstract. This paper describes how the cash-point service can be specified and simulated using Esterel Studio.