Marius Bozga

Modeling Heterogeneous Real-time Components in BIP

We present a methodology for modeling heterogeneous real-time components. Components are obtained as the superposition of three layers: behavior, specified as a set of transitions; Interactions between transitions of the behavior; Priorities, used to choose amongst possible interactions. A parameterized binary composition operator is used to compose components layer by layer. We present the BIP language for the description and composition of layered components as well as associated tools for executing and analyzing components on a dedicated platform. The language provides a powerful mechanism for structuring interactions involving rendezvous and broadcast. We show that synchronous and timed systems are particular classes of components. Finally, we provide examples and compare the BIP framework to existing ones for heterogeneous component-based modeling

Kronos: A model-checking tool for real-time systems

KRONOS is a software tool aiming at assisting designers of real-time systems to develop projects meeting the specified requirements. One major objective of KRONOS is to provide a verification engine to be integrated into design environments for real-time systems in a wide range of application areas. Real-time communication protocols, timed asynchronous circuits and hybrid systems are some examples of application domains where KRONOS has already been used. KRONOS has been also used in analysing real-time systems modeled in several other process description formalisms, such as ATP, AORTA, ET-LOTOS, and T-ARGOS. On the other direction, the tool itself provides an interface to untimed formalisms such as labeled-transition systems (LTS) which has been used to exploit untimed verification techniques.

Tools and Applications II: The IF Toolset

This paper presents an overview on the IF toolset which is an environment for modelling and validation of heterogeneous real-time systems. The toolset is built upon a rich formalism, the IF notation, allowing structured automata-based system representations. Moreover, the IF notation is expressive enough to support real-time primitives and extensions of high-level modelling languages such as SDL and UML by means of structure preserving mappings. The core part of the IF toolset consists of a syntactic transformation component and an open exploration platform. The syntactic transformation component provides language level access to IF descriptions and has been used to implement static analysis and optimisation techniques. The exploration platform gives access to the graph of possible executions. It has been connected to different state-of-the-art model-checking and test-case generation tools. A methodology for the use of the toolset is presented at hand of a case study concerning the Ariane-5 Flight Program for which both an SDL and a UML model have been validated.Finite automata and regular languages have been useful in a wide variety of problems in computing, communication and control, including formal modeling and verification. Traditional automata do not admit an explicit modeling of time, and consequently, timed automata [2] were introduced as a formal notation to model the behavior of real-time systems. Timed automata accept timed languages consisting of sequences of events tagged with their occurrence times. Over the years, the formalism has been extensively studied leading to many results establishing connections to circuits and logic, and much progress has been made in developing verification algorithms, heuristics, and tools. This paper provides a survey of the theoretical results concerning decision problems of reachability, language inclusion and language equivalence for timed automata and its variants, with some new proofs and comparisons. We conclude with a discussion of some open problems.

Rigorous Component-Based System Design Using the BIP Framework

An autonomous robot case study illustrates the use of the behavior, interaction, priority (BIP) component framework as a unifying semantic model to ensure correctness of essential system design properties.

The IF toolset

This paper presents an overview on the IF toolset which is an environment for modelling and validation of heterogeneous real-time systems. The toolset is built upon a rich formalism, the IF notation, allowing structured automata-based system representations. Moreover, the IF notation is expressive enough to support real-time primitives and extensions of high-level modelling languages such as SDL and UML by means of structure preserving mappings. The core part of the IF toolset consists of a syntactic transformation component and an open exploration platform. The syntactic transformation component provides language level access to IF descriptions and has been used to implement static analysis and optimisation techniques. The exploration platform gives access to the graph of possible executions. It has been connected to different state-of-the-art model-checking and test-case generation tools. A methodology for the use of the toolset is presented at hand of a case study concerning the Ariane-5 flight program for which both an SDL and a UML model have been validated

IF-2.0: A Validation Environment for Component-Based Real-Time Systems

It is widely recognised that the automated validation of complex systems can hardly be achieved without tool integration. The development of the IF-1.0 toolbox [3] was initiated several years ago, in order to provide an open validation platform for timed asynchronous systems (such as telecommunication protocols or distributed applications, in general). The toolbox was built upon an intermediate representation language based on extended timed automata. In particular, this representation allowed us to study the semantics of real-time primitives for asynchronous systems. Currently, the toolbox contains dedicated tools on the intermediate language (such as compilers, static analysers and model-checkers) as well as front-ends to various specification languages and validation tools (academic and commercial ones). Among the dedicated tools, we focused on static analysis (such as slicing and abstraction) which are mandatory for an automated validation of complex systems. Finally, the toolbox was successfully used on several case studies, the most relevant ones being presented in [4].

Programs with lists are counter automata

We address the verification problem of programs manipulating one-selector linked data structures. We propose a new automated approach for checking safety and termination for these programs. Our approach is based on using counter automata as accurate abstract models: control states correspond to abstract heap graphs where list segments without sharing are collapsed, and counters are used to keep track of the number of elements in these segments. This allows to apply automatic analysis techniques and tools for counter automata in order to verify list programs. We show the effectiveness of our approach, in particular by verifying automatically termination of some sorting programs.

Kronos: A Model-Checking Tool for Real-Time Systems

KRONOS [9, 11,8, 21, 17, 4, 3, 10] is a software tool aiming at assisting designers of real-time systems to develop projects meeting the specified requirements. One major objective of KRONOS is to provide a verification engine to be integrated into design environments for real-time systems in a wide range of application areas. Real-time communication protocols [9, 11], timed asynchronous circuits [17,4], and hybrid systems [19,11] are some examples of application domains where KRONOS has already been used. KRONOS has been also used in analyzing real-time systems modeled in several other process description formalisms, such as ATP [18], AORTA [5], ET-LOTOS [9], and T-ARGOS [16]. On the other direction, the tool itself provides an interface to untimed formalisms such as labeled-transition systems (LTS) which has been used to exploit untimed verification techniques [21].

Data-Structures for the Verification of Timed Automata

In this paper we suggest numerical decision diagrams, a bdd-based data-structure for representing certain subsets of the Euclidean space, namely those encountered in verification of timed automata. Unlike other representation schemes, ndds are canonical and provide for all the necessary operations needed in the verification and synthesis of timed automata. We report some preliminary experimental results.

Some Progress in the Symbolic Verification of Timed Automata

In this paper we discuss the practical difficulty of analyzing the behavior of timed automata and report some results obtained using an experimental BDD-based extension of KRONOS. We have treated examples originating from timing analysis of asynchronous boolean networks and CMOS circuits with delay uncertainties and the results outperform those obtained by previous implementations of timed automata verification tools.