Message-passing models of distributed computing vary along numerous dimensions: degree of synchrony, kind of faults, number of faults... One way to deal with this variety is by restricting communication to rounds. This is the setting of the Heard-Of model, which captures many models through predicates on the messages sent in a round and received on time, at this round or before on the receivers. Yet, it is not easy to define the predicate that best captures a given operational model. The question is even harder for the asynchronous case, as unbounded message delay means the implementation of rounds must depend on details of the model. This paper shows that characterising asynchronous models by heard-of predicates is indeed meaningful. This characterization relies on the introduction of delivered predicates, an intermediate abstraction between the informal operational model and the heard-Of predicates. Our approach splits the problem in two steps: first extract the delivered model capturing the informal model, and then characterize the heard-of predicates that can be generated by this delivered model. For the first part, we provide both examples of delivered predicates, and an approach to derive more. It uses the intuition that complex models are a combination of simpler models. We thus define operations like union, succession or repetition that make it easier to build complex delivered predicates from simple ones while retaining expressivity. For the second part, we formalize and study strategies for when to change round. Intuitively, the characterizing predicate of a model is the one generated by a strategy that waits for as much messages as possible, without blocking forever.

中文翻译：

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异步消息传递模型的听到谓词的表征和推导

分布式计算的消息传递模型在许多方面有所不同：同步程度，故障种类，故障数量...处理这种变化的一种方法是将通信限制为轮次。这是Heard-Of模型的设置，该模型通过谓词捕获轮次发送的消息并在接收器上或之前按时接收到的消息中的多个模型。然而，定义最能捕捉给定运营模型的谓词并不容易。对于异步情况，这个问题更加棘手，因为无限制的消息延迟意味着回合的实现必须取决于模型的细节。本文表明，通过听取的谓词表征异步模型确实是有意义的。这种表征依赖于引入的谓词的引入，非正式操作模型和听取谓词之间的中间抽象。我们的方法将问题分为两个步骤：首先提取捕获的模型以捕获非正式模型，然后表征可以由此交付的模型生成的听到的谓词。在第一部分中，我们既提供了交付谓词的示例，又提供了派生谓词的方法。它使用这样的直觉，即复杂模型是简单模型的组合。因此，我们定义了诸如联合，继承或重复之类的操作，这些操作使从简单的谓词构建复杂的交付谓词变得更容易，同时又保留了表达能力。在第二部分中，我们正式确定并研究何时进行轮换的策略。凭直觉