From Sequential Specifications to Eventual Consistency

We address a fundamental issue of interfaces that arises in the context of cloud computing. We define what it means for a replicated and distributed implementation satisfy the standard sequential specification of the data structure. Several extant implementations of replicated data structures already satisfy the constraints of our definition. We describe how the algorithms discussed in a recent survey of convergent or commutative replicated datatypes [17] satisfy our definition. We show that our definition simplifies the programmer task significantly for a class of clients who conform to the CALM principle [10].