基于关系数据库有效地实现RPE查询

各种XML查询语言的共同特点就是利用正则路径表达式(RPE)来导航XML文档的查询。本文结合我们提出的一种新的XML数据的关系存储模式，对有效地实现RPE查询的相关研究工作进行了总结，并提出了两个有效地实现包含连接的索引改进归并连接算法。算法采用索引定位技术、短路技术和预侦技术来减少连接代价。因此，不仅能够在当前上下文计算环境下有效地实现包含连接的计算，而且能够大量地避免包含连接中不必要的扫描和搜索。

Efficient Implementing RPE Queries in an RDBMS

The common feature of the XML query languages is the use of regular path expressions (i.e. RPE) to query XML data. In this paper, we briefly review proposal relational storage schemas for XML documents, which can quickly determine ancestor-descendant relationship between any pair of nodes in the hierarchy of XML data, and effectively supports all query powers in XQuery and keyword searches. We then summary related work for efficient implementation of regular path expression queries based on pre-order lists using an RDBMS. Finally, we develop two algorithms called index improved merge join by using indexing technique, short-circuit technique and pre-spying technique, which are proved to be very efficient by cost analysis. Our algorithms can implement containment joins over the current contexts, and largely avoid useless scanning and seeking over irrelevant fragments of the data for containment joins.