Research on Query and Index for GML Spatial Data
GML空间数据查询与索引机制研究

The differences among traditional GIS data models result in difficulty of spatial data integrating and sharing.Commercial GIS vendors and third parties suggested the data conversion solutions.These methods cannot solve the problem perfectly.Geography Markup Language(GML) established by OGC provides standard and framework for spatial data modeling,integrating and sharing.GML has become the defacto international standard for spatial data encoding,transmitting,storing and distributing;more and more spatial data has been stored in GML format.The issue of how to manage the spatial data in GML format efficiently has become the hot one in GIS research.Combining XML database technology and traditional spatial database technology,this paper conducts a deep research on querying and indexing GML data.The spatial extensions to XQuery are suggested.Consequently one GML query language based on XQuery is developed,and native query over GML data is realized.By integrating XML document encoding techniques and traditional spatial index methods,one unified indexing model based on spatial index for GML data is suggested.Taking R-Tree as an example,the performance of the unified indexing model is tested and analyzed through a set of experiments. Experimental results show that the unified indexing model is feasible and efficient.