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.

. 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...