Multi-Guarded Safe Zone: An Effective Technique to Monitor Moving Circular Range Queries

Given a positive value r, a circular range query returns the objects that lie within the distance r of the query location. In this paper, we study the circular range queries that continuously change their locations. We present an efficient and effective technique to monitor such moving range queries by utilising 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. The shape of the safe zone is defined by the so-called guard objects. The cost of checking whether a query lies in the safe zone takes k distance computations, where k is the number of the guard objects. 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) To show the effectiveness of the safe zone, we...

• Type: Conference
• Year: 2010
• Where: ICDE
• Authors: Muhammad Aamir Cheema, Ljiljana Brankovic, Xuemin Lin, Wenjie Zhang, Wei Wang 0011
• Keywords: Circular Range Query, Database, ICDE 2010, Query Location, Safe Zone