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Many fault-tolerant algorithms are based on decisions made by a quorum of nodes. Since the algorithms are utilised in safety critical applications such as distributed databases, it is necessary to make sure that they operate reliably under every possible scenario. We introduce a generic compositional formalism, based on parameterised labelled transition systems, which allows us to express safety properties of parameterised quorum systems. We prove that any parameterised verification task expressible in the formalism collapses into finitely many finite state refinement checking problems. The technique is implemented in a tool, which performs the verification completely automatically. As an example, we prove the leader election phase of the Raft consensus algorithm correct for an arbitrary number of terms and for a cluster of any size.

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Interface theories (ITs) enable us to analyse the compatibility interfaces and refine them while preserving their compatibility. However, most ITs are for finite state interfaces, whereas computing systems are often parametrised involving components, the number of which cannot be fixed. We present, to our knowledge, the first IT that allows us to specify a parametric number of interfaces. Moreover, we provide a fully algorithmic procedure, implemented in a tool, for checking the compatibility of and refinement between parametrised interfaces. Finally, we show that the restrictions of the technique are necessary; removing any of them renders the refinement checking problem undecidable.