No abstract

We present a strategy for nding algebraic correctness proofs for communication systems. It is described in the setting of CRL 11], which is, roughly, A CP 2, 3] extended with a formal treatment of the interaction between data and processes. The strategy has already been applied successfully in 4] and 10], but was not explicitly identi ed as such. Moreover, the protocols that were veri ed in these papers were rather complex, so that the general picture was obscured by the amount of details. In this paper, the proof strategy is materialised in the form of de nitions and theorems. These results reduce a large part of protocol veri cation to a number of trivial facts concerning data parameters occurring in implementation and speci cation. This greatly simpli es protocol veri cations and makes our approach amenable to mechanical assistance experiments in this direction seem promising. The strategy is illustrated by several small examples and one larger example, the Concurrent Alternating Bit Protocol (CABP). Although simple, this protocol contains a large amount o f i n ternal parallelism, so that all relevant i s s u e s m a k e their appearance. A preliminary version of this paper appeared in Models and Proofs, proceedings of AMAST workshop on Real-Time systems and Op eration Inter-PRC \Mod eles et Preuves", Bordeaux, 1995.

We present an equational veri cation of Milner's scheduler, which w e c hecked by computer. To our knowledge this is the rst time that the scheduler is proof-checked for a general numbern of scheduled processes.

We present a generalization of the classical theory of testing for Mealy machines to a setting of dense real-time systems. A model of timed I O automata is introduced, inspired by the timed automaton model of Alur and Dill, together with a notion of test sequence for this model. Our main contribution is a test generation algorithm for black-box conformance testing of timed I O automata. Although it is highly exponential and cannot be claimed to be of practical value, it is the rst algorithm that yields a nite and complete set of tests for dense real-time systems.