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研究生: 陳志瑋
Chen, Chih-wei
論文名稱: 有效率的連續對在道路網路上移動之物體作 K 個最近鄰居搜尋
Efficient Continuous K-Nearest Neighbor Query over Moving Objects in Road Networks
指導教授: 李強
Lee, Chiang
學位類別: 碩士
Master
系所名稱: 電機資訊學院 - 資訊工程學系
Department of Computer Science and Information Engineering
論文出版年: 2009
畢業學年度: 97
語文別: 中文
論文頁數: 62
中文關鍵詞: 移動物體時間-空間資料庫K 個最近鄰居
外文關鍵詞: spatio-temporal databases, moving objects, K-nearest neighbors
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  • 在時間-空間資料庫(spatio-temporal databases)系統所提供的查詢服務裡, 其中有一項重要的查詢稱之為 continuous K-nearest neighbor query (簡稱為 CKNN query). CKNN query 會判斷出在每個時間點, 查詢者的 K 個最近物體, 而這些物體稱之為查詢者的 K 個最近鄰居 (簡稱為 KNN). 在本篇論文中, 我們研究如何在交通運輸網路 (road network) 上去有效地處理這樣的 CKNN query. 在交通運輸網路中, 判斷 KNNs 的準則是根據物體與查詢者之間的最短道路距離 (shorest network distance) 來作為. 由於物體與查詢者皆隨著時間而移動變化位置, 造成兩者之間的道路距離亦會隨時間而改變. 這意謂著在不同時間點, 查詢者會有不同的 KNN. 我們會先說明目前方法在處理 CKNN query 的一些限制和缺點, 然後再提出一個有效的方法來克服目前方法的限制和缺點. 最後, 我們實作了大量的實驗來驗證我們提出的方法之有效性.

    Continuous K-Nearest Neighbor (CKNN) query is an important type of spatio-temporal queries. A CKNN query is to find among all moving objects the K-nearest neighbors (KNNs) of a moving query object at each timestamp. In this paper, we focus on processing such a CKNN query in road networks, where the criterion for determining the KNNs is the shortest network distance between objects. We first highlight the limitations of the existing approaches, and then propose a cost-effective algorithm, namely the Continuous KNN algorithm, to overcome these limitations. Comprehensive experiments are conducted to demonstrate the efficiency of the proposed approach.

    Abstract i Acknowledgements iii Table of Contents iv Table of Figures vi Table of Tables vii Table of Algorithms viii 1 Introduction 1 2 Related works 7 2.1 Methods for Snapshot KNN Queries . . . . . . . . . . . . . 7 2.2 Methods for Continuous KNN Queries . . . . . . . . . . . 8 3 Data Structures 11 4 Network Distance Calculation 15 5 CKNN Algorithm 20 5.1 Filtering Phase . . . . . . . . . . . . . . . . . . . . . . . . 21 5.2 Refinement Phase . . . . . . . . . . . . . . . . . . . . . . . 25 6 Experimental Evaluation 33 6.1 Experimental Setttings . . . . . . . . . . . . . . . . . . . . 33 6.2 Performance of the CKNN algorithm . . . . . . . . . . . . 35 6.2.1 Effect of query interval length . . . . . . . . . . . . 36 6.2.2 Effect of number of nearest neighbors . . . . . . . . 37 6.2.3 Effect of number of objects . . . . . . . . . . . . . . 39 6.3 The impact of object speed . . . . . . . . . . . . . . . . . 40 7 Conclusions 42 Bibliography 47 Biography

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