OreintXA:一种有效的XQuery查询代数

XQuery是XML查询语言的推荐标准.现有的XQuery处理策略有两种方法,一种是基于核心语法一次一结点的方法,另一种是基于查询代数的一次一集合的方法.单独使用这两种方法都不能很好地处理XQuery查询.一方面,基于核心语法树的方法效率低,而且很难优化,而现有基于代数的方法又不能很好地满足XQuery的过程化查询语言的特性.描述了一个有效的XQuery代数系统--OrientXA.它是在总结现有的基于代数的XQuery查询工作、分析未解决的问题,并吸收了前述的两种策略的思想的基础上提出来的.它第一次提出了构造模式树的概念,其中的构造操作符能体现XQuery的灵活特征.由于操作符具有很强的表达能力,OrientXA能够表达W3C的用例和XMark测试集的所有查询.

OrientXA: An Effective XQuery Algebra

XQuery is the recommended standard for XML Query. XQuery processing strategies can be classified into two categories: core syntax based strategy (node-oriented) and algebra based strategy (set-oriented). Neither of them can handle XQuery well. The syntax based strategy is inefficient and hard to optimize, while the current algebra based strategies can not satisfy the flexible programming characteristics of XQuery. After summarizing the current stage and unsolved problems of former algebra based works, an effective XQuery algebra system, OrientXA, is proposed in this paper, ideas from both strategies are embodied in it. OrientXA introduces the notion of Construct Pattern Tree for the first time. The Construct operator in it materializes the flexible characteristics of XQuery. Corresponding to its expressive operators, it is able to express all the queries in W3C use cases and XMark benchmark.