Issue No. 08 - August (2011 vol. 23)
DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/TKDE.2010.246
Muhammad Aamir Cheema , The University of New South Wales, Sydney
Ljiljana Brankovic , The University of Newcastle, Newcastle
Xuemin Lin , The University of New South Wales, Sydney and NICTA
Wenjie Zhang , The University of New South Wales, Sydney and NICTA
Wei Wang , The University of New South Wales, Sydney and NICTA
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 reevaluated 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 approach is close to optimal and is an order of magnitude faster than a naïve algorithm. 4) We also extend our technique to monitor the queries in a road network. Our algorithm is up to two order of magnitude faster than a naïve algorithm.
Query processing, range queries, spatial data, continuous queries, road network.
X. Lin, W. Zhang, W. Wang, L. Brankovic and M. A. Cheema, "Continuous Monitoring of Distance-Based Range Queries," in IEEE Transactions on Knowledge & Data Engineering, vol. 23, no. , pp. 1182-1199, 2010.