AF: Medium: A Fair Prescription for Partial Synchrony

部分同步是指在计算环境中，通信延迟和处理速度存在定时界限，但对这些界限的了解可能是有限的或未知的。尽管这些界限只是隐式的，但在存在消息丢失和处理器崩溃的情况下，它们仍然可以用于构建可靠的分布式系统。然而，核心问题是部分同步的计时参数应该如何建模、测量和命名。自从大约25年前诞生以来，流行的基于计时学的模型范例已经调用实时作为对消息延迟和处理速度的时间界限建模的正式基础。遗憾的是，这些模型作为对经验分布式系统的描述在本质上是有限的(甚至是有缺陷的)，因为部分同步的特征属性不是时间上的及时性，而是时间上的公平性。本项目正在发展基于时间上公平的概念的部分同步的基本理论。关键的技术创新是，系统故障可以在不公平的执行中被检测到，而不是不及时。这种做法导致了更大的普遍性，因为许多不合时宜的处决仍然是公平的。理论结果编码了公平属性的层次结构，包括技术限制、可表现性和可归约为预言模型。实际结果从经验系统中提取公平模型。对计时模型的综合批判有助于启动更广泛的研究趋势，将重点放在部分同步的基于公平的范式上。

Partial synchrony refers to computing environments where timing bounds exist for communication delays and processing speeds, but knowledge of these bounds may be limited or unknown. Although such bounds are only implicit, they can still be used to advantage for building reliable distributed systems in the presence of message loss and crashed processors. The central problem however, is how timing parameters for partial synchrony should be modeled, measured, and denominated.Since its inception some 25 years ago, the prevailing paradigm of chronometry-based models has invoked real-time as a formal basis for modeling temporal bounds on message delays and process speeds. Unfortunately, such models are intrinsically limited (and even flawed) as descriptions of empirical distributed systems, because the characteristic property of partial synchrony is not chronometric timeliness, but rather chronological fairness.This project is developing a fundamental theory of partial synchrony based on the notion of chronological fairness. The key technical innovation is that system failures can be detected in executions that are unfair, rather than untimely. This approach leads to greater generality because many untimely executions are still fair. Theoretical results codify a hierarchy of fairness properties, including technical limitations, expressivity, and reducibility to oracular models. Practical results extract fairness models from empirical systems. An integrated critique of chronometric models helps to initiate a broader shift in research trends to focus on fairness-based paradigms of partial synchrony.