We propose a calculus for concurrent reversible multiparty sessions, equipped with a flexible choice operator allowing for different sets of participants in each branch. This operator is inspired by the notion of connecting action recently introduced by Hu and Yoshida to describe protocols with optional participants. We argue that this choice operator allows for a natural description of typical communication protocols. Our calculus also supports a compact representation of the history of processes and types, which facilitates the definition of rollback. Moreover, it implements a fine-tuned strategy for backward computation. We present a session type system for the calculus and show that it enforces the expected properties of session fidelity, forward progress and backward progress.

中文翻译：

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具有灵活选择的可逆会话

我们提出了一种并发可逆多方会话的演算，配备了灵活的选择运算符，允许每个分支中的不同参与者集。这个算子的灵感来自于最近由 Hu 和 Yoshida 引入的连接动作概念，用于描述可选参与者的协议。我们认为这个选择运算符允许对典型通信协议的自然描述。我们的演算还支持进程和类型历史的紧凑表示，这有助于回滚的定义。此外，它实现了一种用于反向计算的微调策略。我们提出了一个用于微积分的会话类型系统，并表明它强制执行会话保真度、向前进展和向后进展的预期属性。