XML树模式查询的描述语言及形式语义

Description Language and Formal Semantic of XML Tree Pattern Query

作为XML(extensible markup language)数据查询的核心操作,树模式查询的应用前景广泛,其研究具有重要意义。针对扩展的树模式GTP++(generalized tree pattern)提出了一种树模式描述语言XTPL(XML tree pattern language),采用指称语义方式给出其完整的语义描述,使得形式化方法可以用于分析树模式查询的行为特征,有助于验证XML查询的正确性,以及提高查询处理方法的可靠性和鲁棒性。同时以路径表达式为例,以指称语义的方式给出了从路径表达式提取树模式的算法。

As the core operation of XML （extensible markup language） query, tree pattern query has a broad application prospect. Its study has important significance. This paper presents a tree pattern description language XTPL （XML tree pattern language） for the GTP＋＋ which is extended from generalized tree pattern, and uses denotational semantic to give the complete semantic description of XTPL. The denotational semantic of XTPL makes formal methods can be used for the analysis of tree pattern query in the behavior characteristic. It also conduces to verifying the correctness of XML query, and improves the reliability and robustness of query methods. Then, taking the path expression as an example, this paper presents a tree pattern extraction algorithm described by denotational semantic, which extracts tree pattern from path expressions.