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Concurrency control is one of the main issues in the studies of real-time database systems. Optimistic concurrency control algorithms have the attractive properties of being non-blocking and deadlock-free. However, they have the problems of late conflict detection and transaction restarts. Although the number of transaction restarts is reduced by dynamic adjustment of serialization order in real-time database systems, they are still some unnecessary transaction restarts. In this study, we propose a new method called Transaction Finish Degree (TFD) and a new Multiversion Optimistic Concurrency Control algorithm based on TFD (MVOCC-TFD), which can reduce the number of unnecessary restarts. Theoretical analysis and experimental results demonstrate that the new algorithm can outperform the previous ones.

This study presents the spatio-temporal constraint relationships of moving objects by employing Petri Net technology. The spatial constraints of moving objects are first presented in this study based on the V4I[1] theory, then the temporal constraints for moving objects are presented by applying this theory to temporal aspect. With the proposing of Moving Object Petri Net (MOPN) and Spatial Constraint Petri Net (SCPN) in this study, the spatio-temporal constraint relationships of moving objects are presente

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