Copies convergence in a distributed real-time collaborative environment

In real-time collaborative systems, replicated objects, shared by users, are subject to concurrency constraints. In order to satisfy these, various algorithms, qualified as opðtimistic, [3, 5, 13, 17, 14, 15, 18], have been proposed that exploit the semantic properties of operations to serialize concurrent operations and achieve copy conðvergence of replicated objects. Their drawback is that they either reðquire a condition on user's operations which is hard to verify when possible to ensure, or they need undoðing then redoing operations in some situations. The main purpose of this paper is to present two new algorithms that overðcome these drawbacks. They are based upon the impleðmentation of a continuous global order which enables that condition to be released, and simplifies the operation inteðgration process. In the second algorithm, thanks to deðferred broadcast of operations to other sites, this process becomes even more simplified.

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