Relaxed space bounding for moving objects: A case for the buddy tree

Abstract

Rapid advancements in positioning systems and wireless communications enable accurate tracking of continuously moving objects. This development poses new challenges to database technology since maintaining up-to-date information regarding the location of moving objects incurs an enormous amount of updates. There have been many efforts to address these challenges, most of which depend on the use of a minimum bounding rectangle (MBR) in a multi-dimensional index structure such as R-tree. The maintenance of MBRs causes lock contention and association of moving speeds with the MBRs cause large overlap between them. This problem becomes more severe as the number of concurrent operations increases. In this paper, we propose a "new" simple variant of the Buddy-tree, in which we enlarge the query rectangle to account for object movement rather than use an enlarged MBR. The result is not only elegant, but also efficient, particularly in terms of lock contention. An extensive experimental study was conducted and the results show that our proposed structure outperforms existing structures by a wide margin.