XML结构完整性约束下的路径表达式的最小化

Minimization of Path Expression Under Structural Integrity Constraints for XML

引入了一个XML结构完整性约束体系.这个体系描述了XML文档中节点或路径之间的5种结构关系,包括路径蕴涵、路径同现、路径互斥、必需性包含和排他性包含.给出了这些结构完整性约束的语法和语义定义,并研究了它们在XML查询优化中的作用.基于子路径的概念,提出了有结构完整性约束的路径表达式的最小化算法.该算法以路径蕴涵闭包为工具,不仅可以删除路径表达式的冗余,还可以识别无效路径表达式.实验结果表明了该算法的正确性和有效性.

A system of structural integrity constraints for XML （XSICs） is introduced, which specifies five structural relationships between different paths or nodes in XML documents, including path implication, path cooccurrence, path mutual-exclusion, obligatory inclusion and exclusive inclusion. This paper defines the syntax and semantics of these XSICs, and studies their core role in XML query optimization. Based on the concept of sub-path, this paper proposes an algorithm for minimizing path expression in the presence of XSICs. By using the path implication closure as a tool, the algorithm cannot only effectively eliminate redundant nodes or predicates, but also identify invalid path expressions. Experimental results show the effectiveness and efficiency of the proposed minimization algorithm.