文章基本信息

标题：The Height of Piecewise-Testable Languages with Applications in Logical Complexity
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作者：Prateek Karandikar ; Philippe Schnoebelen
期刊名称：LIPIcs : Leibniz International Proceedings in Informatics
电子版ISSN：1868-8969
出版年度：2016
卷号：62
页码：37:1-37:22
DOI：10.4230/LIPIcs.CSL.2016.37
出版社：Schloss Dagstuhl -- Leibniz-Zentrum fuer Informatik
摘要：The height of a piecewise-testable language L is the maximum length of the words needed to define L by excluding and requiring given subwords. The height of L is an important descriptive complexity measure that has not yet been investigated in a systematic way. This paper develops a series of new techniques for bounding the height of finite languages and of languages obtained by taking closures by subwords, superwords and related operations. As an application of these results, we show that FO^2(A^*, subword), the two-variable fragment of the first-order logic of sequences with the subword ordering, can only express piecewise-testable properties and has elementary complexity.
关键词：Descriptive complexity