On the reaction time of some synchronous systems

This paper presents an investigation of the notion of reaction time in some synchronous systems. A state-based description of such systems is given, and the reaction time of such systems under some classic composition primitives is studied. Reaction time is shown to be non-compositional in general. Possible solutions are proposed, and applications to verification are discussed. This framework is illustrated by some examples issued from studies on real-time embedded systems.Comment: In Proceedings ICE 2011, arXiv:1108.014

A Primitive Execution Model for Heterogeneous Modeling

International audienceHeterogeneous modeling is modeling using several modeling methods. Since many different modeling methods are used in different crafts, heterogeneous modeling is necessary to build a heterogeneous model of a system that takes the modeling habits of the designers into account. A model of computation is a formal description of the behavioral aspect of a modeling method. It is the set of rules that allows to compute the behavior of a system by composing the behaviors of its components. Heterogeneous modeling allows parts of the system to obey some rules while other parts obey other rules for the composition of their behaviors. Computing the behavior of a system which is modeled using several models of computation can be difficult if the meaning of each model of computation, and what happens at their boundary, is not well defined. We propose an execution model that provides a framework of primitive operations that allow to express how a model of computation is interpreted in order to compute the behavior of a model of a system. When models of computation are ``implemented'' in this execution model, it becomes possible to specify exactly what is the meaning of the joint use of several models of computation in the model of a system

Etude des méthodes de conception de composants domaine-polymorphes

Les systèmes embarqués sont utilisés dans plusieurs domaines d'application et mélangent plusieurs technologies, ce qui fait d'eux des systèmes hétérogènes complexes. Ainsi, ils sont composés de sous systèmes dont chacun obéit à un modèle de calcul qui lui est approprié. Les modèles de calcul sont des lois qui régissent les interactions des systèmes.Actuellement, pour exécuter un composant atomique, dont le comportement est spécifié suivant la sémantique d'un modèle de calcul, dite sémantique de spécification, sous différents modèles de calcul, on peut utiliser soit l'approche hiérarchique, soit l'approche non hiérarchique, soit des composants domaine-spécifiques. Un composant domaine spécifique étant un composant dont le fonctionnement correct n'est garanti que sous le modèle de calcul pour lequel il est conçu. Cependant, ces approches présentent plusieurs désavantages.Pour éviter ces problèmes, nous proposons dans cette thèse un nouveau modèle de composant, appelé composant domaine-polymorphe. Un composantdomaine-polymorphe est un composant atomique ayant la capacité d'exécuter son comportement interne suivant la sémantique de spécification tout en garantissant un fonctionnement correct sous différents modèles de calcul. En découplant la sémantique de spécification et celle d'exécution, cette approche offre une bonne modularité. L'adaptation à la sémantique d'exécution étant automatique, ces composants sont facilement réutilisables etparamétrables afin d'expliciter les interactions entre modèles de calcul, ce qui augmente la productivité et facilite la maintenabilité ainsi que le processus de validation.Embedded systems are used in numerous application domains and mix several technologies, what makes them complex and heterogeneous systems. They are composed of subsystems that are designed using a model of computation (MoC) that suits the needs of their designers. The MoCs are the laws that govern the interaction of the components of a subsystem.In order to use an atomic component, the behavior of which is specified according to a given MoC, in a model that obeys a different MoC, we can use the hierarchical approach, the non-hierarchical approach or build a domain-specific component (DSC). Such components obey the MoC for which they have been designed.To overcome these problems, we propose a new model of component, that we call >. Such a component is atomic and able to execute its core behavior, specified under a given MoC, under different host MoCs. By decoupling the semantics of the specification and the semantics of the execution context, our approach provides good modularity. The adaptation to the semantic of execution is automatic, so the domain-polymorph components are easily reusable. It is possible to customize their adaptation to the host MoC in order to get explicit control on the interactionsbetween MoCs, what facilitates the maintainability and the process of validation of the systems.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Modélisation hétérogène non-hiérarchique

Les systèmes embarqués sont naturellement hétérogènes et les outils actuels employés pour leur modélisation utilisent une approche hiérarchique, qui, bien qu'évitant l'explosion combinatoire du nombre d'interfaces entre différents modèles de calcul (MoCs), impose systématiquement un changement de niveau hiérarchique lorsque l'on passe d'un MoC à un autre. Or ce couplage entre la hiérarchie et les changements de MoC perturbe la structure du modèle, nuit à la réutilisabilité des composants, altère la modularité et réduit la maintenabilité des modèles. Cette thèse propose une approche non-hiérarchique qui découple les changements des MoCs de la hiérarchie. Elle repose sur l'utilisation de " Composant à Interface Hétérogène " (Heterogeneous Interface Component - HIC) qui dispose d'entrées et de sorties de natures différentes pour permettre la communication hétérogène dans le système et d'un Modèle d'Exécution Hétérogène Non-Hiérarchique dont la tâche est de restructurer le système en le partitionnant, i.e., en créant des sous-systèmes homogènes à la frontière des comportements hétérogènes, puis, d'ordonnancer leurs activations en déléguant leur ordonnancement interne à leurs MoCs réguliers et d'exécuter le système. Cette approche présente plusieurs avantages : - l'utilisation de plusieurs composants hétérogènes au même niveau hiérarchique, - la séparation entre le flot de contrôle et le flot de données qui augmente la réutilisabilité des composants. - la spécification par le concepteur du comportement de son système à la limite des différents MoCs comme partie intégrante du système contribue efficacement à la modularité et à la maintenabilité des modèles.Embedded systems are naturally heterogeneous. Currently, modeling tools used for modeling embedded systems use a hierarchical approach. This approach although avoiding the combinatorial explosion of the number of interfaces between models of Computation (MoCs) forces the change of hierarchical level when passing from one MoC to another. But, this coupling between hierarchy and model changing perturbs the structure of the model, affects the modularity and makes difficult the maintainability of the model. Moreover this coupling is harmfull to the reuse of the component.This thesis proposes a new approach that dissociates the MoC from this hierarchy. This approach uses two components : a "Heterogeneous Interface Components (HIC) " and a "Non-Hierarchical Heterogeneous Execution Model". A HIC have inputs and outputs of different nature to allow the heterogeneous communication in a system. The Execution Model reorganizes the system by partitionning, i.e. by creating homogenous subsystems at the border of the heterogeneous behavior. It schedules the activation of those subsystems and delegates their internal scheduling to their regular MoC. Finally it executes the system. This approach presents several advantages : the use of several components that use heterogeneous inputs or outputs at the same level of the hierarchy.The separation of control flow and data flow increases the reuse of the components.The explicit specification of the heterogeneous behavior of the system at the boundary between different MoCs as an integral part of the system, contributes efficiently to the modularity and the maintainability of the models.ORSAY-PARIS 11-BU Sciences (914712101) / SudocFONTAINEBLEAU-MINES ParisTech (771862302) / SudocSudocFranceF

On Teaching the Concept of Refinement

The concept of refinement is central to the development of software. It appears in various forms in the different methodologies taught to students. A key point in the B method is the validation of the refinement step. The B methodology exhibits mathematical properties of correct refinements, and also automatically checkable conditions that ensure those properties. Some of the main pedagogical difficulties that the present authors found in teaching B centered around the notions linked to refinement, at the conceptual level, and at the tool level. Many papers have been published on the general benefits of the B method. This paper will focus on the specific concepts linked to refinements, and on the ones which need special care. We argue that, although B presents a complete mathematical analysis, it is beneficial to put the concept of refinement in perspective with other theories that come from formal methods, namely, in this paper, coalgebra and bisimulation. Keywords: Coalgebra, Gluing invariant, Morphism, Refinement

Synchronous Reactive Programming in Ptolemy

Synchronous reactive languages allow a high level deterministic description of reactive systems such as control-command systems. Their well defined mathematical semantics makes it possible to check formal properties on the control of a system. In previous work, we developed an object-oriented execution model for synchronous reactive modules. This model is implemented as a set of tools and a C++ class library, and allows us to use object-oriented methodologies and tools for the design of complex applications with both transformational and reactive parts. Among these design tools, the Ptolemy system stands as an object-oriented framework that supports various execution models, or "domains". We are currently working on a translator from the output format of the Lustre and Esterel compilers to the Ptolemy language. Since no existing domain matches the reactive synchronous execution model, we also plan to develop a SEC (Synchronous Execution and Communication) domain. Such a domain will provi..

A Multi-Level Framework for Validation of Ontology-Driven and Community-Based Web Services Composition

International audienceThis paper proposes an Ontology-driven and Community-based Web Services (OCWS) framework which aims at automating discovery, composition and execution of web services. The purpose is to validate and to execute a user's request built from the composition of a set of OCWS descriptions and a set of user constraints. The defined framework separates clearly the OCWS external descriptions from internal realistic implementations of e-services. It identifies three levels: the knowledge level, the community level and e-services level and uses different participant agents deployed in a distributed architecture. First, the reasoner agent uses a description logic extended for actions in order to reason about: (i) consistency of the pre-conditions and post-conditions of OCWS descriptions and the user constraints with ontologies semantics, (ii) consistency of the workflow matching assertions and the execution dependency graph. Then the execution plan model is generated automatically to be run by the composer agents using the dynamic execution plan algorithm (DEPA), according to the workflow matching and the established execution order. The community composer agents invoke the appropriate e-services and ensure that the non functional constraints are satisfied. DEPA algorithm works dynamically without a priori information about e-services states and has interesting properties such as taking into account the non-determinism of e-services and reducing the search space

ANALYSE COMPORTEMENTALE DE SYSTEMES COMPLEXES CRITIQUES PAR PRODUIT SYNCHRONISE D'ABSTRACTIONS EN RESEAUX DE PETRI ORDINAIRES D'AGENTS TEMPS-REEL

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF