分布式异构空间数据共享研究

在构建防震减灾WebGIS体系的过程中，引入GML来描述空间数据，设计了空间数据库系统，以实现多源异构数据的共享。系统基于客户层、服务器层和数据库服务器三层体系结构来建造。客户层实现图形用户界面并完成数据的表示。服务器包括Web服务器和GIS应用服务器，前者主要用以客户端通信、后者则要实现对数据库服务器的访问，多源空间数据的获取、转换和输出标准的GML文件等。数据库服务器用来存放本地数据和链接分布式异构数据库。系统采用Java Servlet来完成Web服务器和GIS应用服务器的功能开发，通过Java applet实现客户端、并利用SVG来实现GML数据的可视化。

STUDY OF DISTRIBUTED HETEROGENEOUS SPATIAL DATA SHARING

In the process of constructing WebGIS based earthquake disaster reduction, the Geography Markup language (GML) is used to represent spatial data, and the spatial database system is designed to realize the sharing of heterogeneous data. The system is composed of three-tier architecture, client, server and database server. The client tier realizes graphics user interface and represents spatial data. The server includes Web server and GIS application server. The former is used to communicate with client-side, and the latter is used to access database server. The conversion and output of GML document are also in charge of by GIS application server. The local data and the distributed heterogeneous database lie in database server. The Web server and GIS application server are developed using Java Servlet. And the client-side is developed using Java Applet. Moreover, scalable vector graphics (SVG) is used to visualize the GML data.