Spatial Queries in the Presence of Obstacles Jun Zhang, Dimitris Papadias, Kyriakos Mouratidis, and Manli Zhu   View Paper (PDF)   Return to Session 7: Query Processing Techniques for Spatial Databases Abstract Despite the existence of obstacles in many database applications, traditional spatial query processing utilizes the Euclidean distance metric assuming that points in space are directly reachable. In this paper, we study spatial queries in the presence of obstacles, where the obstructed distance between two points is defined as the length of the shortest path that connects them without crossing any obstacles. We propose efficient algorithms for the most important query types, namely, range search, nearest neighbors, e-distance joins and closest pairs, considering that both data objects and obstacles are indexed by R-trees. The effectiveness of the proposed solutions is verified through extensive experiments. ©2005 Association for Computing Machinery