Efficient MaxCount and threshold operators of moving objects
Geoinformatica
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Computer controlled systems contribute to safety in transportation systems and many other critical life-saving and life-support systems. Part 1 presents the implementation and exploration of arbitrarily precise semantic approximations for software verification using over-approximation and under-approximation techniques in constraint databases. The approximations are implemented in the MLPQ system and several program examples are analyzed in comparison to previous results. Part 2 presents novel MAXCOUNT, THRESHOLDRANGE, THRESHOLDC OUNT, THRESHOLDSUM, THRESHOLD AVERAGE and COUNTRANGE estimation algorithms for moving points in d dimensions and a new spatiotemporal bucketing technique for indices. Each query runs in constant time and is based on skew-aware static size buckets. This bucket technique allows constant time inserts, deletes and updates needed for highly dynamic spatiotemporal databases. The technique is also decomposable to allow partial results to be calculated simultaneously and recombined in linear time. We performed extensive experiments that show these threshold aggregation estimation algorithms run up to 35 times faster than a precise algorithm with accuracy above 95%.