Mobile Agent-based Spatial Data Sharing

The rapid application of networking GIS (Geographical Information System) has provided a great convenience for social production and people's daily life. However, it also brings into being the problem of GIS isolated island inevitably, and has resulted in a huge waste of GIS resource. Therefore, sharing geospatial data distributed on the net is significant for increasing work efficiency and saving producing cost, especially, to build National Spatial Information Infrastructure and Digital Earth.First, the dissertation introduces the current situation of geospatial data sharing. Ease of use, interoperation is the main difficulties in sharing geospatial data on the net. And then presents the studies of foreign and domestic consortiums, corporations and university.Second, by discussing current patterns of sharing geospatial data, the author comes to a conclusion that it must be developed in a open and interoperable way Then, this paper deeply studies related technologies including geospatial metadata, GML, SVG and Mobile Agent, and their advantages to geospatial data sharing.Third, the paper studies the advantages and disadvantages of the existing 3-tire map expressing in web environment. Then, the author puts forward a 4-tire geospatial data expressing system, which consists of abstract map, virtual map, concrete map and visual map. These open technologies will play a critical role in constructing geospatial data sharing system.Fourth, by using the brand-new Mobile Agent, an architecture of geospatial data sharing based on Mobile Agent is designed, which clearly compartmentalized the tires in the 4-tire geospatial data expressing system. The architecture consists of Web Browser, Web Server, Metadata MA Server, Map MA Server, and Data MA Server. By the interaction of these four parts, it can created abstract map, virtual map, concrete map and visual map. The Web Browser generates map request for user, updates the initial virtual map, and display visual map. The main functionality of Web Server is to generate abstract map and concrete map. Metadata MA server as directory of Map MA Server provides service of generating virtual map, registering metadata, and updating metadata. Data MA Server is in charge of providing related geospatial data for Map MA Server.Finally, based on the above schema, a prototype system is developed, and pseudo code is presented to describe its implementation. To test correction and feasibility of the schema, a test in the prototype system, which requests traffic-related geospatial data of Zhangdian district of Zibo, Shandong province, is implemented and the satisfied result is achieved.