Abstract The Concurrency Workbench is an automated tool for analyzing networks of finite-state processes expressed in Milner's Calculus of Communicating Systems. Its key feature is its breadth: a variety of different verification methods, including equivalence checking, preorder checking, and model checking, are supported for several different process semantics. One experience from our work is that a large number of interesting verification methods can be formulated as combinations of a small number of primitive algorithms. The Workbench has been applied to the verification of communications protocols and mutual exclusion algorithms and has proven a valuable aid in teaching and research. 1 Introduction This paper describes the Concurrency Workbench [11, 12, 13], a tool that supports the automatic verification of finite-state processes. Such tools are practically motivated: the development of complex distributed computer systems requires sophisticated verification techniques to guarantee correctness, and the increase in detail rapidly becomes unmanageable without computer assistance. Finite-state systems, such as communications protocols and hardware, are particularly suitable for automated analysis because their finitary nature ensures the existence of decision procedures for a wide range of system properties.

We present a method for the compositional construction of the minimal transition system that represents the semantics of a given distributed system. Our aim is to control the state explosion caused by the interleavings of actions of communicating parallel components by reduction steps that exploit global communication constraints given in terms of interface specifications. The effect of the method, which is developed for bisimulation semantics here, depends on the structure of the distributed system under consideration, and the accuracy of the interface specifications. However, its correctness is independent of the correctness of the interface specifications provided by the program designer.

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Higher-order process calculi, for its abstraction capability and theoretical significance, have constantly been receiving much attention in the field of process calculi, and stand as a mathematical tool for describing and analyzing mobile systems with dynamically changing inter-connection structures. In this thesis we contribute to the higher-order paradigm in several aspects. • Higher-order π-calculus with mismatch: the bisimulation theory. Linear fragment of higherorder π-calculus with mismatch: the axiomatization. The problem of the axiomatization of higher-order process calculi, such as higher-order πcalculus, is always a non-trivial one. However, it is important, both in theory and practice, to be able to decide whether two higher-order processes are equivalent with respect to some bisimulation, which needs an algorithm that can effectively analyze and give an answer efficiently. We further the available work by considering the higher-order π-calculus with mismatch, which is a useful operator in bisimulation theory and especially the axiomatization, from algorithmic point of view. We first formulate the bisimulation theory, where the bisimulation we define is called open weak higher-order bisimulation, which is a non-delayed