Contribution to the verification of timed automata (determinization, quantitative verification and reachability in networks of automata)

Cette thèse porte sur la vérification des automates temporisés, un modèle bien établi pour les systèmes temps-réels. La thèse est constituée de trois parties. La première est dédiée à la déterminisation des automates temporisés, problème qui n'a pas de solution en général. Nous proposons une méthode approchée (sur-approximation, sous-approximation, mélange des deux) fondée sur la construction d'un jeu de sûreté. Cette méthode améliore les approches existantes en combinant leurs avantages respectifs. Nous appliquons ensuite cette méthode de déterminisation à la génération automatique de tests de conformité. Dans la seconde partie, nous prenons en compte des aspects quantitatifs des systèmes temps-réel grâce à une notion de fréquence des états acceptants dans une exécution d'un automate temporisé. Plus précisément, la fréquence d'une exécution est la proportion de temps passée dans les états acceptants. Nous intéressons alors à l'ensemble des fréquences des exécutions d'un automate temporisé pour étudier, par exemple, le vide de langages seuils. Nous montrons ainsi que les bornes de l'ensemble des fréquences sont calculables pour deux classes d'automates temporisés. D'une part, les bornes peuvent être calculées en espace logarithmique par une procédure non-déterministe dans les automates temporisés à une horloge. D'autre part, elles peuvent être calculées en espace polynomial dans les automates temporisés à plusieurs horloges ne contenant pas de cycles forçant la convergence d'horloges. Finalement, nous étudions le problème de l'accessibilité des états acceptants dans des réseaux d'automates temporisés qui communiquent via des files FIFO. Nous considérons tout d'abord des automates temporisés à temps discret, et caractérisons les topologies de réseaux pour lesquelles l'accessibilité est décidable. Cette caractérisation est ensuite étendue aux automates temporisés à temps continu.This thesis is about verification of timed automata, a well-established model for real time systems. The document is structured in three parts. The first part is dedicated to the determinization of timed automata, a problem which has no solution in general. We propose an approximate (over-approximation/under-approximation/mix) method based on the construction of a safety game. This method improves both existing approaches by combining their respective advantages. Then, we apply this determinization approach to the generation of conformance tests. In the second part, we take into account quantitative aspects of real time systems thanks to a notion of frequency of accepting states along executions of timed automata. More precisely, the frequency of a run is the proportion of time elapsed in accepting states. Then, we study the set of frequencies of runs of a timed automaton in order to decide, for example, the emptiness of threshold languages. We thus prove that the bounds of the set of frequencies are computable for two classes of timed automata. On the one hand, we prove that bounds are computable in logarithmic space by a non-deterministic procedure in one-clock timed automata. On the other hand, they can be computed in polynomial space in timed automata with several clocks, but having no cycle that forces the convergence between clocks. Finally, we study the reachability problem in networks of timed automata communicating through FIFO channels. We first consider dicrete timed automata, and characterize topologies of networks for which reachability is decidable. Then, this characterization is extended to dense-time automata.RENNES1-Bibl. électronique (352382106) / SudocSudocFranceF

Counterexample-based refinement for a boundedness test for CFSM languages

Abstract. In precursory work we suggested an abstraction-based highly scalable semi-test for the boundedness of Communicating Finite State Machine (CFSM) based modelling and programming languages. We illustrated its application to Promela and UML-RT models. The test is sound with respect to determining boundedness, but may return inconclusive ”counterexamples ” when boundedness cannot be established. In this paper we turn to the question how to effectively determine the spuriousness of these counterexamples, and how to refine the abstraction based on the analysis. We employ methods from program analysis and illustrate the application of our refinement method to a number of Promela examples.

Embedded System Design

A unique feature of this open access textbook is to provide a comprehensive introduction to the fundamental knowledge in embedded systems, with applications in cyber-physical systems and the Internet of things. It starts with an introduction to the field and a survey of specification models and languages for embedded and cyber-physical systems. It provides a brief overview of hardware devices used for such systems and presents the essentials of system software for embedded systems, including real-time operating systems. The author also discusses evaluation and validation techniques for embedded systems and provides an overview of techniques for mapping applications to execution platforms, including multi-core platforms. Embedded systems have to operate under tight constraints and, hence, the book also contains a selected set of optimization techniques, including software optimization techniques. The book closes with a brief survey on testing. This fourth edition has been updated and revised to reflect new trends and technologies, such as the importance of cyber-physical systems (CPS) and the Internet of things (IoT), the evolution of single-core processors to multi-core processors, and the increased importance of energy efficiency and thermal issues

Embedded System Design

A unique feature of this open access textbook is to provide a comprehensive introduction to the fundamental knowledge in embedded systems, with applications in cyber-physical systems and the Internet of things. It starts with an introduction to the field and a survey of specification models and languages for embedded and cyber-physical systems. It provides a brief overview of hardware devices used for such systems and presents the essentials of system software for embedded systems, including real-time operating systems. The author also discusses evaluation and validation techniques for embedded systems and provides an overview of techniques for mapping applications to execution platforms, including multi-core platforms. Embedded systems have to operate under tight constraints and, hence, the book also contains a selected set of optimization techniques, including software optimization techniques. The book closes with a brief survey on testing. This fourth edition has been updated and revised to reflect new trends and technologies, such as the importance of cyber-physical systems (CPS) and the Internet of things (IoT), the evolution of single-core processors to multi-core processors, and the increased importance of energy efficiency and thermal issues