基于路径表达式的XML索引查询技术

XML index query technology based on path expression

为减少结构连接操作时对输入数据大小的依赖、在大部分实际情况下提高算法效率,研究了当前结构连接算法产生大量中间结果而导致过多连接次数的问题,提出一种新的基于结构摘要的索引技术。对路径树和XML树分别编码,使用少量预先计算的路径信息。在结构连接时执行交叉操作,该操作由位图在较短时间内实现,并且只返回结点所在路径的位置信息,减少了I/O次数。实验结果表明了其具有较高的查询效率,并且查询时间不依赖于输入数据的规模。

In order to minimize the dependence on input size when structural joins are evaluated,and thereby obtain an algorithm likely to be very fast in most real situations,the problem that the current structural join algorithm produces a large number of intermediate results which led to excessive number of structural connectivity is researched.A new indexing method based on the structure summary is pre-sented.Path Tree and XML Tree are encoded on different coding schema.A small amount of pre-computed path information is used.It is based on using intersection operation in evaluating the join.The intersection is done over a bitmap index which results in a small evaluation time.In the implementation of the structural join operation,only returns the location of the node in the path.It effectively reduced I/O times.At last experiment proved its high efficiency and the evaluation time is independent of input size.