Research And Implementation Of Spatial Data Model Based On XML

Spatial data model is the theoretical foundation of spatial data organization and process in GIS. It is has a decisive role in GIS's development. The rapid development of Internet makes the needs for the access to spatial information increasingly evident. The retrieval to spatial data through a browser has gone deep into people's daily life. A new application named WebGIS appears. Therefore, it is an inevitable trend to propose a spatial data model for Web environment.Firstly, this paper introduces theories of the spatial cognition and the data model, analysies adventage and disadvantage of the three typical spatial data model, points out the strengths of the object-oriented data model, then proposes a spatial data model for Web environment. Unlike conventional feature-oriented spatial data model, the entity-oriented spatial data model based on XML proposed in this paper provides three sub models as concept-oriented model, entity-oriented model and feature-oriented model, and stores spatial entity in an object-oriented way, in order to be in line with people's congnition to the geographic world and avoid the layer compositing operation during the entity query. It gives the detail definition and design of the three-tier data model as well as the mapping between models, stores the data with XML and applies a good solution to data sharing.This model integrates and improves the basic spatial analysis method, such as topology analysis, orientation analysis and measurement analysis. Then this paper proposes the entity-oriented spatial analysis method in order to fit the semantics of the real world. It reduces the calculated amount and improves the algorithm' performance.Finally, we complete a fully functional WebGIS system with Dalian University of Technology main campus and its surroundings as a complete geographical space and give a reasonable division of the above area. This system uses a fat-client architecture and XML-SVG-based vector map format, stores data in an entity-oriented way, implements four modules, such as layer control, map operation, information query and spatial analysis,and gives an effective support to the spatial data model based on XML.