DISTRIBUTED SYNCHRONIZATION OF GROUP OPERATIONS IN COOPERATIVE EDITING ENVIRONMENTS

This paper proposes a novel distributed algorithm for synchronizing gr oup operations which maintain consistency of shared documents in coope rative editing environments. In the proposed algorithm, dependent oper ations are closely synchronized so that they are executed in the same causal order at all sites. Independent operations are executed asynchr onously as soon as they arrive. In particular, local editing operation s can be executed immediately, leading to good responsiveness: Moreove r, despite the possible out-of-total-order execution of independent gr oup operations, a totally ordered consistent view of the shared docume nts is maintained at all sites when the system is at quiescent. Each s ite makes decisions on operation ordering and synchronization based on its local status and piggybacked information in incoming requests, an d no centralized coordinator or locks are used. Therefore, the algorit hm is fully distributed without a single point of failure or performan ce bottleneck. Preliminary simulation and experimentation have shown t hat the basic mechanisms used in out algorithm are correct, effective, and efficient.