Faster Deciding MSO Properties of Trees of Fixed Height, and Some Consequences
Faster Deciding MSO Properties of Trees of Fixed Height, and Some Consequences
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更快地确定固定高度树木的 MSO 特性以及一些后果
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发表时间:
2012
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通讯作者:
Petr Hliněný
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作者:
Jakub Gajarský;Petr Hliněný
We prove, in the universe of trees of bounded height, that for any MSO formula with $m$ variables there exists a set of kernels such that the size of each of these kernels can be bounded by an elementary function of m. This yields a faster MSO model checking algorithm for trees of bounded height than the one for general trees.
From that we obtain, by means of interpretation, corresponding results for the classes of graphs of bounded tree-depth (MSO_2) and shrub-depth (MSO_1), and thus we give wide generalizations of Lampis' (ESA 2010) and Ganian's (IPEC 2011) results. In the second part of the paper we use this kernel structure to show that FO has the same expressive power as MSO_1 on the graph classes of bounded shrub-depth. This makes bounded shrub-depth a good candidate for characterization of the hereditary classes of graphs on which FO and MSO_1 coincide, a problem recently posed by Elberfeld, Grohe, and Tantau (LICS 2012).