Specification and Implementation of Replicated List: The Jupiter Protocol Revisited

The replicated list object has been frequently used to model the core functionality (e.g., insertion, deletion, and read) of replicated collaborative text editing systems. In this paper we revisit the specification and implementation of a replicated list object, specifically the weak list specification proposed recently by Attiya et al. and the Jupiter protocol designed in the 1990s. We prove that Jupiter indeed satisfies the weak list specification, solving the conjecture of Attiya et al. To address the mismatch between the global property of weak list specification and the local views each replica maintains in the Jupiter protocol, we propose the CSS (Compact State-space) Jupiter protocol, which at a high level, maintains only a single novel n-ary ordered state-space for a client/server system with n clients. By contrast, the original Jupiter protocol, we call the CSCW protocol, needs to maintain 2n 2D state-spaces where replica states are dispersed. We first show that the CSS protocol and the CSCW protocol are equivalent in the sense that their behaviors are the same under the same schedule of operations/messages. Then, we prove that the CSS protocol satisfies the weak list specification.