Value-Based Sequential Consistency for Set Objects in Dynamic Distributed Systems

This paper introduces a shared object, namely a set object that allows processes to add and remove values as well as take a snapshot of its content. A new consistency condition suited to such an object is introduced. This condition, named value-based sequential consistency, is weaker than linearizability. The paper also addresses the construction of a set object in a synchronous anonymous distributed system where participants can continuously join and leave the system. Interestingly, the protocol is proved correct under the assumption that some constraint on the churn is satisfied. This shows that the notion of "provably correct software" can be applied to dynamic systems.