文章基本信息

标题：Containment for Conditional Tree Patterns
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作者：Alessandro Facchini ; Yoichi Hirai ; Maarten Marx 等
期刊名称：Logical Methods in Computer Science
印刷版ISSN：1860-5974
电子版ISSN：1860-5974
出版年度：2015
卷号：11
期号：2
页码：1
DOI：10.2168/LMCS-11(2:4)2015
出版社：Technical University of Braunschweig
摘要：A Conditional Tree Pattern (CTP) expands an XML tree pattern with labels attached to the descendant edges. These labels can be XML element names or Boolean CTPs. The meaning of a descendant edge labelled by A and ending in a node labelled by B is a path of child steps ending in a B node such that all intermediate nodes are A nodes. In effect this expresses the until B, A holds construction from temporal logic.This paper studies the containment problem for CTP. For tree patterns (TP), this problem is known to be coNP-complete. We show that it is PSPACE-complete for CTP. This increase in complexity is due to the fact that CTP is expressive enough to encode an unrestricted form of label negation: ${*}\setminus a$, meaning "any node except an a-node". Containment of TP expanded with this type of negation is already PSPACE-hard. CTP is a positive, forward, first order fragment of Regular XPath. Unlike TP, CTP expanded with disjunction is not equivalent to unions of CTP's. Like TP, CTP is a natural fragment to consider: CTP is closed under intersections and CTP with disjunction is equally expressive as positive existential first order logic expanded with the until operator.
其他关键词：XPath, XML, Conditional Tree Pattern, Containment, Complexity.