基于XML数据的通用路径表达式的查询

The Query of Currency Path Expression Based on XML Data

查询重写是数据库研究的一个基本问题,它和查询优化、数据仓库、数据集成、语义缓存等数据库问题密切相关。同时,查询重写也是在关系数据库中存储和查询XML数据的关键问题。由于XML数据是元素嵌套和元素引用的,嵌套层数可以任意,并且模式和数据混合,因此XML的查询会涉及到广义路径表达式(GPE)。文中着重研究了如何解决XML数据的查询重写的方案,把含有广义路径表达式的XML查询语句重写为含有简单路径表达式(SPE)的XML查询语句,再转化为基于关系数据库的SQL语句。

Query rewriting is a basic problem in database research. It is relevant to many aspects of database management, including query optimization, datawarehouse, data integration, semantic cache, etc. At the same time, it is a key problem to store and query XML data on DBMS. Because XML data are element embedding and quoting, the number of embedding tiers can be arbitrary, query in XML data involve to GPE. In this paper, a method of query rewriting is included, which change an XML query sentence contained GPE into another XML query sentence contained SPE, at last into SQL sentence on DBMS.