The Research And Implementation Of GIServices Based On Web Technology

With the rapid developments of the Web technology, GIS has entered a brand-new stage. Web technologies give geographic information a big drive so that it can be more open and pupullar to the public, industries and departments. At present, web technology has extended from distributed technology to grid. It gives the web a new chance and also makes GIS turn from system to service. Web GIServices is also an important branch on GIServices research.This paper summarizes the current Web GIS research results and indicates that GIS should turn to service pattern step by step. The paper analyzes the phylogeny of the web technology & web GIS and explains the developments and successful examples of GIServices in our countries and abroad. Communications are needed between web communication and different kinds of applications. Based on communication, we particular expound the WS (Web Services) technology and study the relations between WS and web GIServices. Then we raise a conception of web GIServices under open environment and the applied rules of services on demand.The paper elucidates the service system, basic structure, frame-work of web GIServices. What's more, We categorize the web GIServices into 5 systems and analyzes its basic flow. The paper elucidates the service system, basic structure, frame-work of web GIServices. According to web environment, it points out the conceptions and categorizes of broad sense & narrow sense GIServices and classifies the two kinds of web GIServices and analyzes them for instance. Among them, We lay emphisis on classical web GIServices based on C/S & B/S and new web GIServices under open environment, e.g. distributed GIServices, agent GIServices, grid GIServices. We analyze the three factors that influence the capabilities of web GIServices. According to services's abilities, the paper put web GIServices into a category of strong & tiny web GIServices. Then the paper introduces W3C's XML technology and SVG, which expands XML to vector graphics. XML and its expansibility are very important to open web GIServices research. The thesis shows OGC's Web GISercices system and its OWS plan, including three basic service types: WMS, WFS and WCS. All these services all use GML, which expands XML to GIS, as their communication interfaces.The paper presents the communication specification and mechanism of web GIServices based on XML, including the methods of sheets and styles that validate XML's validity. The paper presents the communication specification and mechanism of web GIServices based on XML. We explain the geographic encoding and parsing based on XML, especially XML's DOM parsing. After encoding the geographic attribute data with CyberXML deifined by ourselves, we build the relation between spatial data and attribute CyberXML data. By using the J2EE system, we illustrate an example on CyberXML GIServices.The paper also introduces SVG specification, including its features, properties. When analyzing the possibility of geographic information encoding and visiualization with SVG, we point out the principles of SVG geographic encoding. Utilizing these principles, we encode thegeometrical data and attribute data and get a SVG encoding map. The parsing of SVG is another question. We study the DOM parsing method of SVG and parse the SVG encoding data mentioned above. With a feasible DOM parsing method we build and the script programming language, we establish an archetype SVG GIServices system which can run with the standard IE browser. It is very complex to design a full XML solution.The final purpose of GIServices is the service to applications. The thesis paints a blueprint of GIService application. Its main goal is the integration with the current existing department information system. Superiorities when dapatment information applications are associated with GIServices in data exchange, function developing is described. The paper studies ESRI's AppLink technology, integration methods of geographic information application and department information application. At last, two department mangement information systems with the heavy support of GIServices are realized. One is commerce physical distribution platform. The other is electronic business platform. Some decision-making functions based on GIServices, including spatial analysis and data exchange, are carried out.At last, the paper summarizes the content of the web GIServices. The paper also applies a few research directions on web GIServices for future study and gives a simple expectation about web GIServices.