An Index mechanism for multi-scale view in spatial databases

作     者：ZHANGYuan-zhi XIEKun-qing MAXiu-jun LIChen-yu CHENZhuo 

作者机构：DepartmentofComputerSciencePekingUniversityBeijing100871P.R.China DepartmentofIntelligenceSciencePekingUniversityBeijing100871P.R.China BeijingInstituteofSurveyingandMappingBeijing100038P.R.China 

出 版 物：《重庆邮电学院学报（自然科学版）》 (Journal of Chongqing University of Posts and Telecommunications(Natural Sciences Edition))

年 卷 期：2004年第16卷第5期

页      面：16-22页

学科分类：081203[工学-计算机应用技术] 08[工学] 0835[工学-软件工程] 0812[工学-计算机科学与技术（可授工学、理学学位）] 

基　　金：This work is supported by the Major Project of National Natural Science Foundation (4 0 2 35 0 5 6 ) andthe Major Project of Natural Science Foundation of Beijing(4 0 110 0 2 ) 

主　　题：索引机制 空间数据库 多级观察 R树 可见性 选择性 简单性 

摘      要：There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations: retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R tree. The difference between the generalization and the R tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value, too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub blocks, and vertexes are total ordered by their importance value. With the help of the generalized R tree, one can easily retrieve data at different detail levels. Some experiments are performed on real life data to evaluate the performance of solutions that separately use normal spatial index and multi scale spatial index. The results show that the solution using multi scale index in SISP is satisfying.