We present a calculus of mobile processes without prefix or summation, and using two different encodings we show that it can express both action prefix and guarded summation. One encoding gives a strong correspondence but uses a match operator; the other yields a slightly weaker correspondence but uses no additional operators.

We report on our experience in using the Isabelle/HOL theorem prover to mechanize proofs of observation equivalence for systems with infinitely many states, and for parameterized systems. We follow the direct approach: An infinite relation containing the pair of systems to be shown equivalent is defined, and then proved to be a weak bisimulation. The weak bisimilarity proof is split into many cases, corresponding to the derivatives of the pairs in the relation. Isabelle/HOL automatically proves simple cases, and guarantees that no case is forgotten. The strengths and weaknesses of the approach are discussed.

We introduce a notion of bisimulation for graph rewriting systems, allowing us to prove observational equivalence for dynamically evolving graphs and networks. We use the framework of synchronized graph rewriting with mobility which we describe in two different, but operationally equivalent ways: on graphs defined as syntactic judgements and by using tile logic. One of the main results of the paper says that bisimilarity for synchronized graph rewriting is a congruence whenever the rewriting rules satisfy the basic source property. Furthermore we introduce an up-to technique simplifying bisimilarity proofs and use it in an example to show the equivalence of a communication network and its specification.

We study behavioural equivalences for dynamic web data in Xd#, a model for reasoning about behaviour found in (for example) dynamic web page programming, applet interaction, and web-service orchestration. Xd# is based on an idealised model of semistructured data, and an extension of the #-calculus with locations and operations for interacting with data. The equivalences are non-standard due to the integration of data and processes, and the presence of locations. Contents 1

The aim of this thesis is to describe the semantics of a process calculus by means of hypergraph rewriting, creating a specification mechanism combining modularity of process calculi and locality of graph transformation. Verification of processes is addressed by presenting two methods: barbed congruence for relating processes displaying the same behaviour and generic type systems, forming a central part of this work. Based on existing work in graph rewriting...

We study the use of the π-calculus for semantical descriptions of languages such as Concurrent Idealised ALGOL (CIA), combining imperative, functional and concurrent features. We first present an operational semantics for CIA, given by SOS rules and a contextual form of behavioural equivalence; then a π-calculus semantics. As behavioural equivalence on π-calculus processes we choose the standard (weak early) bisimilarity. We compare the two semantics, demonstrating that there is a close operational correspondence between them and that the π-calculus semantics is sound. This allows for applying the-calculus theory in proving behavioural properties of CIA phrases. We discuss laws and examples which have served as benchmarks to various semantics, and a more complex example involving procedures of higher order.

. The aim of this paper is to advocate the use of bisimulation relations in the verication of innite-state or parameterized systems, and demonstrates the support that general-purpose theorem provers can oer. A powerful proof technique, known as up to expansion, is discussed and applied in a case study about write invalidate cache coherence. This example is of interest, as the system is parameterized in the number of its components, and the bisimulation relation reects the coherence of the caches with the main memory. 1 Introduction In recent years, general-purpose theorem proving has come to play an important role in the verication of concurrent systems, especially for systems which are too large to be treated fully automatically, or even innite. Yet, if one is not to use the tool as a mere proof checker, some attention has to be spent on the choice of a suitable methodology. (1) Although generalpurpose theorem provers like Isabelle, PVS, or Coq, oer a considerable amount of au...

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

Observation equivalence is a well-known technique for proving that a concurrent system satises its specication. We report on our experience in the mechanization of observation equivalence proofs with the help of a general-purpose theorem prover. Several case-studies are considered, incluiding an sliding window and a cache-coherence protocol. In all cases the system has an innite number of states, and sometimes also an arbitrarily large number of components. We show how compositionality and bisimulation-up-to techniques can be applied to reduce the size of the proofs. 1 Introduction One of the main goals of the A3 Teilprojekt within the Sonderforschungsbereich 342 is the development of verication techniques for distributed systems. Since 1995, special emphasis has been put on automatic (model-checking) and semi-automatic techniques, and in the period 1998-2000, A3 has devoted special attention and resources to the development of machine support for the analysis of systems ...