J.C.M. Baeten

Applications of process algebra

1. An introduction to process algebra J. A. Bergstra and J. W. Klop 2. Two simple protocols F. W. Vaandrager 3. Proving mutual exclusion with process algebra E. R. Nieuwland 4. Process algebra as a tool for the specification and verification of CIM-architectures S. Maauw 5. A process creation mechanism in process algebra J. A. Bergstra 6. Correctness proofs for systolic algorithms: palindromes and sorting L. Kossen and W. P. Weijland 7. Verification of an algorithm for log-time sorting by square comparison J. C. Mulder and W. P. Weijland 8. On the Amoeba protocol J. C. Mulder 9. Process algebra semantics of Popl F. W. Vaandrager 10. Some observations of redundancy in a context F. W. Vaandrager 11. A modular approach to protocol verification using process algebra C. P. J. Koymans and J. C. Mulder.

Analyzing a Chi model of a turntable system using Spin, CADP, and Uppaal

Nowadays, due to increasing system complexity and growing competition and costs, industry makes high demands on powerful techniques used to design and analyze manufacturing systems. One of the most popular techniques to do performance analysis is simulation. However, simulation-based analysis cannot guarantee the correctness of a system, so it is less suitable for functional analysis. Our research focuses on examining other methods to do performance analysis and functional analysis, and trying to combine the two. One of the approaches is to translate a simulation model that is used for performance analysis to a model written in an input language of an existing verification tool. We translate a χ [D.A. van Beek, K.L. Man, M.A. Reniers, J.E. Rooda, R.R.H. Schiffelers, Syntax and Consistent Equation Semantics of Hybrid Chi, CS-Report 04-37, Eindhoven University of Technology, 2004] simulation model of a turntable system into models written in the input languages of the tools CADP [J.-C. Fernandez, H. Garavel, A. Kerbrat, L. Mounier, R. Mateescu, M. Sighireanu, CADP—a protocol validation and verification toolbox, in: Proceedings of the 8th Conference on Computer Aided Verification (CAV’96), Lecture Notes in Computer Science, vol. 1102, 1996, pp. 437–440], Spin [G.J. Holzmann, The SPIN Model Checker, Addison-Wesley, 2003] and Uppaal [K.G. Larsen, P. Pettersson, W.Yi, Uppaal in a nutshell, Int. J. Software Tools for Technology Transfer 1 (1–2) (1997) 134–152] and do a functional analysis with each of them. This allows us to evaluate the usefulness of these tools for the functional analysis of χ models. We compare the input formalisms, the expressiveness of the temporal logics, and the algorithmic techniques for model checking that are used in those tools.

A characterization of regular expressions under bisimulation

We solve an open question of Milner [1984]. We define a set of so-called well-behaved finite automata that, modulo bisimulation equivalence, corresponds exactly to the set of regular expressions, and we show how to determine whether a given finite automaton is in this set. As an application, we consider the star height problem.

Integration of Supervisory Control Synthesis in Model-Based Systems Engineering

Increasing system complexity, time to market and development costs reduction place higher demands on engineering processes. Formal models play an important role here because they enable the use of various model-based analyses and early integration techniques and tools. Engineering processes based on formal models are able to cope with complexity. They also support time to market and development costs reduction. Moreover, application of supervisory control synthesis in the development of control systems can speed up the process considerably. This paper discusses the integration of recently developed supervisor synthesis techniques and tools in engineering processes. To illustrate this approach, examples of industrial cases are presented, where supervisors synthesized have successfully been implemented and integrated in existing resource control platforms.

Model-based Engineering of Embedded Systems Using the Hybrid Process Algebra Chi

Hybrid Chi is a process algebra for the modeling and analysis of hybrid systems. It enables modular specification of hybrid systems by means of a large set of atomic statements and operators for combining these. For the efficient implementation of simulators and the verification of properties of hybrid systems it is convenient to have a model that uses a more restricted part of the syntax of hybrid Chi. To that purpose the linearization of a reasonably expressive, relevant subset of the Chi language is discussed. A linearization algorithm that transforms any specification from this subset into a so-called normal form is presented. The algorithm is applied to a bottle-filling line example to demonstrate tool-based verification of Chi models.

Axiomatizing probabilistic processes : ACP with generative probabilities

This paper is concerned with finding complete axiomatizations of probabilistic processes. We examine this problem within the context of the process algebra ACP and obtain as our end-result the axiom system prACP I −- , a probabilistic version of ACP which can be used to reason algebraically about the reliability and performance of concurrent systems. Our goal was to introduce probability into ACP in as simple a fashion as possible. Optimally, ACP should be the homomorphic image of the probabilistic version in which the probabilities are forgotten.

Regular expressions in process algebra

We tackle an open question of Milner (1984). We define a set of so-called well-behaved finite automata that, modulo bisimulation equivalence, corresponds exactly to the set of regular expressions.

The Total Order Assumption

The total order assumption (TOA) is the assumption that all execution sequences of observable actions or events are totally ordered by precedence. As long as in some cases TOA is to the point, total order and partial order semantics are both legitimate but lead to different theories. I argue that TOA is a simplifying assumption, and present an example of a total order theory without interleaving, and a partial order theory with interleaving.

Reconciling real and stochastic time: the need for probabilistic refinement

We conservatively extend an ACP-style discrete-time process theory with discrete stochastic delays. The semantics of the timed delays relies on time additivity and time determinism, which are properties that enable us to merge subsequent timed delays and to impose their synchronous expiration. Stochastic delays, however, interact with respect to a so-called race condition that determines the set of delays that expire first, which is guided by an (implicit) probabilistic choice. The race condition precludes the property of time additivity as the merger of stochastic delays alters this probabilistic behavior. To this end, we resolve the race condition using conditionally-distributed unit delays. We give a sound and ground-complete axiomatization of the process theory comprising the standard set of ACP-style operators. In this generalized setting, the alternative composition is no longer associative, so we have to resort to special normal forms that explicitly resolve the underlying race condition. Our treatment succeeds in the initial challenge to conservatively extend standard time with stochastic time. However, the ‘dissection’ of the stochastic delays to conditionally-distributed unit delays comes at a price, as we can no longer relate the resolved race condition to the original stochastic delays. We seek a solution in the field of probabilistic refinements that enable the interchange of probabilistic and nondeterministic choices.

An MSC Based Representation of DiCons

We present a graphical MSC-based representation of the language DiCons, which is a formal language for the description of Internet applications.