An Efficient Index Structure for Spatial Databases

Abstract

In this paper, the authors propose an efficient spatial data structure called the Multi-R tree. The Multi-R tree is an improvement of the R-tree, R+-tree and R*-tree, and can be used as an index structure for spatial databases. The Multi- R tree improves performance by distributing spatial objects into several data spaces instead of one data space in the Rtree, the R+-tree or the R*-tree. Each data space is associated with a tree in the Multi-R tree. The structure of the Multi-R tree eliminates the node redundancy which appears in the R+-tree at leaf level and keeps disjoint intermediate rectangles. A set of new algorithms for the Multi-R tree is also proposed and implemented. Three popular spatial data structures, the R-tree, R+-tree and R*-tree, are implemented based on the algorithms given in original literature to be compared with the Multi-R tree. An experimental performance analysis for four implemented structures is given with various types of testing data sets: random data, uniformly distributed data, VLSI layout data and TIGER/Line file. Namely, the number of disk accesses and actual response time for each of those four data structures to process a query are compared. Construction times, space utilization and actual memory sizes of the four data structures are also given. Results show that the Multi-R tree requires fewer disk accesses and less processing time than the R-tree, R+-tree and the R*-tree do for a deletion operation and answering a range query in most cases except for a point query or a range query with very small size. In the cases of a point query or small size query processing, the performance of the Multi-R tree is still better than the performances of the Rtree and R*-tree but slightly worse than the R+-tree. Thus, the Multi-R tree may be used as an efficient index structure for spatial databases, e.g., geographical information system, CAD, and VLSI etc.