- Title
- Multi-guarded safe zone: an effective technique to monitor moving circular range queries
- Creator
- Cheema, Muhammad Aamir; Brankovic, Ljiljana; Lin, Xuemin; Zhang, Wenjie; Wang, Wei
- Relation
- 2010 IEEE 26th International Conference on Data Engineering (ICDE 2010). 26th IEEE International Conference on Data Engineering, ICDE: Conference Proceedings (Long Beach, CA 1-6 March, 2010) p. 189-200
- Publisher Link
- http://dx.doi.org/10.1109/ICDE.2010.5447864
- Publisher
- Institute of Electrical and Electronics Engineers (IEEE)
- Resource Type
- conference paper
- Date
- 2010
- Description
- 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 theoretically evaluate the probability that a query leaves the safe zone within one time unit and the expected distance a query moves before it leaves the safe zone. Additionally, for the queries that have diameter of the safe zone less than its expected value multiplied by a constant, we also give an upper bound on the expected number of guard objects. This upper bound turns out to be a constant, that is, it does not depend either on the radius r of the query or the density of the objects. The theoretical analysis is verified by extensive experiments. 3) Our thorough experimental study demonstrates that our proposed approach is close to optimal and is an order of magnitude faster than a naïve algorithm.
- Subject
- access order; guard objects; moving circular range queries; multiguarded safe zone; pruning rules; query monitoring
- Identifier
- http://hdl.handle.net/1959.13/927150
- Identifier
- uon:10058
- Identifier
- ISBN:9781424454440
- Rights
- Copyright © 2010 IEEE. Reprinted from the 26th IEEE International Conference on Data Engineering, ICDE: Conference Proceedings. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Newcastle's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.
- Language
- eng
- Full Text
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