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Service Availability in Concurrent Systems - Part I: A Theory of Hierarchical Services of Interacting Processes

Service Availability in Concurrent Systems—Part I: A Theory of Hierarchical Services of Interacting Processes. M.S. FALLAH AND A.R. SHARAFAT The paper introduces an axiomatic model of concurrent systems through which a number of issues related to service availability including mutual exclusion, deadlock/starvation freedom, denial/quality of services and fault tolerance can be described in a cohesive manner. The paper starts from the claim that existing formal models of concurrent systems are not suited for the analysis of service availability. It develops the hierarchical services of interacting processes (HSIP) model which allows a system to be viewed both as a set of processes and as a set of services. Similarities between HSIP and CSP are outlined. The authors explain the three components that form a concurrent system in HSIP: the hierarchy, the timing and the computation model. The system hierarchy identifies the atomic services required in a system execution. The system timing and the system computation model enable the identification of the instants at which atomic services are requested. The paper gives the axioms that represent the availability of resources and atomic services and illustrates through examples the usefulness of HSIP in modelling concurrent systems. In a follow up [1], the authors analyse further the problem of system availability.