嵌套关系演算和XQuery中的良定性和语义类型检查
Well-Definedness and Semantic Type-Checking in the Nested Relational Calculus and XQuery
摘要：
关于XML查询语言XQuery的两个自然的决策问题是良好定义和语义类型检查。我们研究这些问题的设置的关系片段的XQuery。我们表明，良好的定义和语义类型检查是不可判定的，即使在积极存在的情况下。然而，对于XQuery的“pure”变体，其中在项目和包含该项目的单例之间没有标识，问题变得可判定。我们还考虑了嵌套关系演算中的类似问题。
英文摘要：
Two natural decision problems regarding the XML query language XQuery are well-definedness and semantic type-checking. We study these problems in the setting of a relational fragment of XQuery. We show that well-definedness and semantic type-checking are undecidable, even in the positive-existential case. Nevertheless, for a ``pure'' variant of XQuery, in which no identification is made between an item and the singleton containing that item, the problems become decidable. We also consider the analogous problems in the setting of the nested relational calculus.
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