Continuous Monitoring of Distance Based Range Queries

Given a positive value r, a distance based range query returns the objects that lie within the distance r of the query location. In this paper, we focus on the distance based range queries that continuously change their locations in a Euclidean space. We present an efficient and effective monitoring technique based on the concept of a safe zone. The safe zone of a query is the area with a property that while the query remains inside it, the results of the query remain unchanged. Hence, the query does not need to be re-evaluated unless it leaves the safe zone. Our contributions are as follows. 1) We propose a technique based on powerful pruning rules and a unique access order which efficiently computes the safe zone and minimizes the I/O cost. 2) We theoretically determine and experimentally verify the expected distance a query moves before leaving the safe zone and, for majority of queries, the expected number of guard objects. 3) Our experiments demonstrate that the proposed ...

• Type: Journal
• Year: 2011
• Where: TKDE
• Authors: Muhammad Aamir Cheema, Ljiljana Brankovic, Xuemin Lin, Wenjie Zhang, Wei Wang
• Keywords: Continuous Query, Range Queries, Road Network, Safe Region, Safe Zone, Spatial Network, Spatial Queries