Probabilistic Time Consistent Queries over Moving Objects

Xiang Lian, Lei Chen

Abstract: Recently, the wide usage of inexpensive mobile devices, along with broad deployment of wireless and positioning technology, has enabled many important applications such as Delay Tolerant Networks (DTN). In these applications, the positions of mobile nodes are dynamically changing, and are often imprecise due to the inaccuracy of positioning devices. Therefore, it is crucial to efficiently and effectively monitor mobile nodes (modeled as uncertain moving objects). In this paper, we propose a novel query, called probabilistic time consistent query (PTCQ). In particular, a PTCQ retrieves uncertain moving objects that consistently satisfy query predicates within a future period with high confidence. We present effective pruning methods to reduce the search space of PTCQs, and seamlessly integrate them into an efficient query procedure. Moreover, to facilitate query processing, we specifically design a data structure, namely UC-Grid, to index uncertain moving objects. The structure construction is based on a formal cost model to minimize the query cost. Extensive experiments demonstrate the efficiency and effectiveness of our proposed approaches to answer PTCQs.