GML空间数据查询与索引机制研究

由于传统GIS数据模型的差异，导致空间数据难以集成与共享。各GIS软件厂商及第三方软件厂商提出了利用空间数据转换的解决方案，但是它还是不能很好地解决空间数据集成与共享存在的问题。地理标记语言GML的出现，为GIS空间数据建模、集成与共享提供了统一的标准与框架。GML已经成为事实上的空间数据编码、传输、存储和发布的国际标准，大量GML格式的空间数据开始涌现。如何有效地存储管理GML空间数据，已经成为GIS研究的热点问题。本文结合XML数据库技术和传统的空间数据库技术，对GML空间数据的查询、索引进行了深入的研究。以XML标准查询语言XQuery为基础，提出了XQuery空间扩展的内容，开发了GML空间数据查询语言，实现了GML空间数据的本原查询；结合XML文档编码和传统的空间数据索引，提出了基于空间索引的GML一体化索引机制，并以R树索引为例，对一体化索引的查询处理性能进行了实验分析。实验结果表明，本文提出的基于空间索引的GML一体化索引机制是可行的、高效的。

Research on Query and Index for GML Spatial Data

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.