XML数据的路径表达式查询优化技术

Optimizing Path Expression Queries of XML Data

路径表达式作为XML数据查询语言的核心部分,关于它的计算方法的研究成果已有很多,然而针对路径表达式本身进行优化的研究却相对较少.提出了两种针对路径表达式的优化策略:路径缩短策略和补路径策略,从而提高了XML路径查询效率.路径缩短策略根据XML文档模式信息,将路径表达式查询长度缩短,从而简化查询本身以降低需要的查询代价;而补路径策略则试图使用代价更小的等价路径表达式来替换原始查询.经过对实验数据的分析,这两种优化策略对于绝大多数路径表达式查询可以应用,并可大幅度地改进路径表达式的查询性能.

Path expression is one of the core components of most XML query languages, and many evaluation methods for path expression queries are proposed recently. However, there are few researches on the issue of path expression optimization. Two kinds of path expression optimizing principles are proposed, named path shorten and path complementing, respectively. The path shorten principle reduces the querying cost by shortening the path expressions with the knowledge of XML schema. While the path complementing principle tends to substitute the user queries with the equivalent lower-cost path expressions. The experimental results show that these two techniques can work on most path expression queries and largely improve the efficiency of path expression query processing.