Characterization and Derivation of Heard-Of Predicates for Asynchronous Message-Passing Models

In distributed computing, multiple processes interact to solve a problem together. The main model of interaction is the message-passing model, where communicate by exchanging messages. Nevertheless, there are several models varying along important dimensions: degree synchrony, kinds faults, number faults... This variety compounded lack general formalism in which abstract these models. One way bring order constrain rounds. setting Heard-Of captures many through predicates on messages sent round and received time. Yet, it not easy define predicate that given operational model. question even harder for asynchronous case, as unbounded message delay means implementation rounds must depend details paper shows characterising heard-of indeed meaningful. characterization relies delivered predicates, an intermediate abstraction between informal predicates. Our approach splits into two steps: first extract capturing then characterize generated this For part, we provide examples derive more. It uses intuition complex composition simpler We operations like union, succession or repetition make easier from simple ones while retaining expressivity. second formalize study strategies when change Intuitively, characterizing one strategy waits much possible, without blocking forever.