The Rely { Guarantee Method forVerifying Shared Variable

Compositional proof systems for shared variable concurrent programs can be devised by including the interference information in the speciica-tions. The formalism falls into a category called rely{guarantee (or assumption{ commitment), in which a speciication is explicitly (syntactically) split into two corresponding parts. This paper summarises existing work on the rely-guarantee method and gives a systematic presentation. A proof system for partial correct-ness is given rst, thereafter it is demonstrated how the relevant rules can be adapted to verify deadlock freedom and convergence. Soundness and completeness , of which the completeness proof is new, are studied with respect to an operational model. We observe that the rely{guarantee method is in a sense a reformulation of the classical non-compositional Owicki & Gries method, and we discuss throughout the paper the connection between these two methods.