The CGI Design And Implementation Of WebGIS Based On XML

With the development of internet technology, the application of GIS (Geographic Information System) is being gradually upgraded from desktop application to network application. Especially, with the extensive use of Internet, the spatial information resource on the network is broadened continually, and at present or in the future, all kinds of spatial information services are or will be supplied through tens of thousands web sites. Moreover, through the technical conformity of internet and geographic information, spatial information's share and interoperation can be realized by visiting and handling the information islands constructed by special GIS platform formerly, which are independent, relatively close, and unable to communicate and collaborate with each other.In recent years, with the rapidly development of the computer technologies, how to share spatial data through network becomes the primary research task of Web GIS. The main purpose of Web GIS is to realize the issue of spatial geographic information and data sharing on the Internet, to make user be able to access GIS data straightway via web browser, and to execute such GIS functions as query, statistics, edit and creating thematic map of geographic data and business logic data. The appearance of XML technologies bring Internet a new developing chance, which has been paid more attention to by IT enterprises for its structuralization, extensibility and flexibility, and its developing prospect is promising. As far as Web GIS is concerned, XML can be used in standard storage for spatial data, data sharing, network transmission, electric map displaying and GIS software framework building.In this paper, challenges faced by traditional Web GIS in such aspects as spatial geographic information issue on the Internet and spatial interoperation are pointed out, and the problems as how to express and handle spatial data and how to solve the interoperation among several different Web GIS applying XML technologies are described in details. The research work is done for such problems as spatial data storage, network transmission, data sharing and interoperation in Web GIS research and exploitation. The primary research target is to establish a web service system for geographic data issue based on SVG, GML and SOAP/Web Service technologies, and to establish a CGI-based Web GIS service system. The main research work are summarized: geographic spatial data storage and sharing in GML format, SVG format encoding and visualization; geographic spatial data organization and conformity with object-oriented relation database; the data parsing and format transforming among GML, SVG and Shape file; a general framework establishingand a prototype development of Web GIS server software system in a multi-tiered distribute structure utilizing SOAP/Web Service.Based on the data organization and the architecture design of Web GIS, a multi-tiered distributing Web GIS prototype system is developed, and the CGI design of Web GIS is implemented. Using the campus map as the geographic data source, a network test for the map issue on the Internet is executed here. OGC and W3C corresponding open standards are conformed to in the prototype system design, and some international specifications are consulted for the system design and realization. Some characteristics of this prototype system are as follows: GML and SVG format applying in geographic data expressing, dynamic data loading according to scale, one downloading and many times using of geographic data and data's granular updating.In a word, XML related technologies present much superiority in the Web GIS application and development. In the future, XML could be the base of the information technology, and also be the base for Web GIS developing. It is believed that more and more GIS technology specifications and system tools should be developed and designed based on XML technology in the near future, for its great potentialities in the future Internet's development.