Research On Issues Of Consistency Algorithm For Replicated Continuous Interactive Media

With the fast development of computer science and technology, replicated continuous interactive media such as Distributed Virtual Environment (DVE), Networked Computer Games, Collaborative Virtual Environment (CVE), Distributed Interactive Simulation (DIS), Computer Supported Cooperative Work (CSCW), etc. have been developed rapidly and used widely. The consistency maintenance has been the focus of research on replicated continuous interactive media for long period of time. Local-lag algorithm is a very effective way of consistency maintenance and it could avoid short time inconsistency. However, there are some negative effects of local lag algorithm on continuous interactive media. In this paper, it has been proved that local-lag algorithm will lead the happening of context violation. When context violation happens, the state of the media when an operation is issued will be different with the state when it is being executed. Therefore, the execution results in the various states might be different from each other. In this case, result violation happens.In order to study the effects of context violation on execution result in local-lag algorithm, an "X-Spaceship" networked computer game has been developed to serve as the experiment platform. The experimental results show that result violation does happen, as proved by theory. Besides, the probability of result violation's happening will increase with the lag value. The increase rates are different when different lag values are selected.Since "Echo" is a very effective way to enhance the interactive effects in the system that adopted the local-lag algorithm. Another group of experiment has also been done to investigate the effects of context violation on execution result of local-lag algorithm that adopted the "Echo" method. Besides, experiments have been done to compare the probability of result violation happening with "Echo" and without "Echo" at the same lag value. The experimental result shows that probability of result violation happening will also increase with lag value when "Echo" is used. Meanwhile, although "Echo" could not decrease the happening of result violation lead by context violation,it dose make users feel helpful to avoid the negative effect of result violation.The research of this thesis will give a guide to the usage of local lag in continuous interactive media. Besides, it could also provide the directions for future research on local lag algorithm.