A Functional Rephrasing of the Assumption Commitment Speci cation Style

The assumption commitment also called rely guarantee style has been advocated for the speci cation of interactive components of distri buted systems One of its motivations is to achieve modularity for state transition speci cations of system components It suggests the structuring of speci cations into assumptions about the behavior of the component s environment and into commitments that are ful lled by the component provided the environment ful lls these assumptions We de ne the as sumption commitment formats for functional system speci cations In particular we work out a canonical decomposition of system speci ca tions following the assumption commitment format into safety and live ness aspects We demonstrate the format of assumption commitment speci cations by a number of examples In particular we discuss the methodological signi cance of the assumption commitment format in the stepwise development of speci cations This work was partially supported by the Sonderforschungsbereich Werkzeuge und Methoden f ur die Nutzung paralleler Rechnerarchitekturen