Hendrik Brinksma

An Algebraic Approach to the Specification of Stochastic Systems (Extended Abstract)

We introduce a framework to study stochastic systems, i.e. systems in which the time of occurrence of activities is a general random variable. We introduce and discuss in depth a stochastic process algebra (named ♤) adequate to specify and analyse those systems. In order to give semantics to ♤, we also introduce a model that is an extension of traditional automata with clocks which are basically random variables: the stochastic automata model. We show that this model and ♤ are equally expressive. Although stochastic automata are adequate to analyse systems since they are finite objects, they are still too coarse to serve as concrete semantic objects. Therefore, we introduce a type of probabilistic transition system that can deal with arbitrary probability spaces. In addition, we give a finite axiomatisation for ♤ that is sound for the several semantic notions we deal with, and complete for the finest of them. Moreover, an expansion law is straightforwardly derived.

Developments in Testing Transition Systems

This paper discusses some of the developments in the theory of test generation from labelled transition systems over the last decade, and puts these develxadopments in a historical perspective. These developments are driven by the need to make testing theory applicable to realistic systems. We illustrate the developments that have taken place in a chronological order, and we discuss the main motivations that led to these developments. In this paper the claim is made that testing theory (slowly) narrows the gap with testing practice, and that progress is made in designing test generation algorithms that can be used in realistic situations while maintaining a sound theoretical basis.

Managing the Verification Trajectory

Abstract.In this paper we take a closer look at the automated analysis of designs, in particular of verification by model checking. Model checking tools are increasingly being used for the verification of real-life systems in an industrial context. In addition to ongoing research aimed at curbing the complexity of dealing with the inherent state space explosion problem – which allows us to apply these techniques to ever larger systems – attention must now also be paid to the methodology of model checking, to decide how to use these techniques to their best advantage. Model checking “in the large” causes a substantial proliferation of interrelated models and model checking sessions that must be carefully managed in order to control the overall verification process. We show that in order to do this well both notational and tool support are required. We discuss the use of software configuration management techniques and tools to manage and control the verification trajectory. We present Xspin/Project, an extension to Xspin, which automatically controls and manages the validation trajectory when using the model checker Spin.

Enhancements of Lotos

In this chapter we present an overview of enhancements of the ISO specification language LOTOS that have been proposed in the Lotosphere project. The detailed proposals Management and Evaluation of Language Development can be found in [D07].

Prozessalgebra, Teil 1

Abstract Dieser Beitrag beinhaltet eine Einführung in die Prozessalgebra. Im ersten Teil wird eine Basis-Prozessalgebra vorgestellt und informell die Bedeutung ihrer Operatoren erläutert. Im zweiten Teil des Artikels beschreiben wir, wie prozessalgebraische Ausdrücke als Transitionssysteme interpretiert werden können. Anhand des Roboter-Beispiels der Artikelserie werden die elementaren Konzepte illustriert. Ein Kernstück der Prozessalgebra, beobachtbares Verhalten verschiedener Prozesse zu vergleichen, wird erläutert. Der Beitrag schließt mit einem kleinen Überblick über verschiedene Richtungen in der Prozessalgebra.