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Supporting Range Queries on Web Data Using k -Nearest Neighbor Search. Wan D. Bae, Shayma Alkobaisi, Seon Ho Kim, Sada Narayanappa Computer Science, University of Denver and Cyrus Shahabi Computer Science, University of Southern California. W2GIS 2007. Outline. Introduction
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Supporting Range Queries on Web Data Usingk-Nearest Neighbor Search Wan D. Bae, Shayma Alkobaisi, Seon Ho Kim, Sada Narayanappa Computer Science, University of Denver and Cyrus Shahabi Computer Science, University of Southern California W2GIS 2007
Outline • Introduction • Motivation and Approach • Quad Drill Down (QDD) Algorithm • Dynamic Constrained Delaunay Triangulation (DCDT) Algorithm • Experiments • Conclusions W2GIS 2007
Motivation • Large volume of geospatial data available on the web. • Access limited by certain types of queries: • e.g., nearest neighbor queries • Utilize available queries to answer non-supported queries. W2GIS 2007
Range Query Find all McDonalds’ locations in a given rectangular region W2GIS 2007
Range Queries on Web Data using k Nearest Neighbor Search W2GIS 2007
Objective and Approaches Find all objects within a given rectangular query range using a minimum number of k-NN searches • Quad Drill Down (QDD) • Dynamic Constrained Delaunay Triangulation (DCDT) W2GIS 2007
Quad Drill Down (QDD) algorithm W2GIS 2007
Quad Drill Down (QDD) algorithm q1 q2 q q 3-NN search q3 q4 W2GIS 2007
Dynamic Constrained Delaunay Triangulation (DCDT) algorithm W2GIS 2007
DCDT algorithm • A greedy and incremental approach • Use Constrained Delaunay Triangulation (CDT) (a) (b) W2GIS 2007
DCDT 1stk-NN call CDT select uncovered max propagate k-NN call checkCoverRegion W2GIS 2007
DCDT – coverRegion (a) (b) (c) W2GIS 2007
CoverRegion Examples (a) (b) (c) (d) (e) (f) W2GIS 2007
Propagation (a) (b) (c) (d) (e) (f) W2GIS 2007
QDD vs. DCDT vs. N.C. Synthetic data set w/3% range qeury W2GIS 2007
QDD vs. DCDT vs. N.C. Synthetic data set w/3% range qeury W2GIS 2007
Percentage of Coverage Varying k value W2GIS 2007
Conclusions Propose two algorithms to find all objects within a given rectangular query range using k-NN searches: • Quad Drill Down (QDD) • Dynamic Constrained Delaunay Triangulation (DCDT) W2GIS 2007
Thank you! W2GIS 2007