Abstracting Communication to Reason about Distributed Algorithms

ing Communication to Reason about Distributed Algorithms? Michel Charpentier, Mamoun Filali, Philippe Mauran, G erard Padiou, Philippe Qu einnec LIMA IRIT, ENSEEIHT 2, rue Charles Camichel 31071 Toulouse cedex, FRANCE e-mail: fcharpov,mauran,padiou,[email protected], [email protected] Abstract. In distributed systems, message passing is a low level representation of communication resulting in intricate designs and proofs. This paper presents a new abstraction to express communication: the observation. This notion provides a more concise expression of programs and properties, and consequently is an e ective help in understanding and reasoning about distributed algorithms. Observations are formalized in the Unity framework. We de ne the observation relation and state its main properties. Then, we present the description and the proof of a generic problem. The abstract level of description separates concerns between the algorithm and its communication pattern. Thus, the topology of observations can be changed while preserving the algorithm properties.