When trees grow low: shrubs and fast MSO1

  • Authors:
  • Robert Ganian;Petr Hliněný;Jaroslav Nešetřil;Jan Obdržálek;Patrice Ossona de Mendez;Reshma Ramadurai

  • Affiliations:
  • Institute for Informatics, Goethe University, Frankfurt, Germany;Faculty of Informatics, Masaryk University, Brno, Czech Republic;Computer Science Inst. of Charles University (IUUK), Praha, Czech Republic;Faculty of Informatics, Masaryk University, Brno, Czech Republic;École des Hautes Études en Sciences Sociales, CNRS UMR 8557, Paris, France;Faculty of Informatics, Masaryk University, Brno, Czech Republic

  • Venue:
  • MFCS'12 Proceedings of the 37th international conference on Mathematical Foundations of Computer Science
  • Year:
  • 2012

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Abstract

Recent characterization [9] of those graphs for which coloured MSO2 model checking is fast raised the interest in the graph invariant called tree-depth. Looking for a similar characterization for (coloured) MSO1, we introduce the notion of shrub-depth of a graph class. To prove that MSO1 model checking is fast for classes of bounded shrub-depth, we show that shrub-depth exactly characterizes the graph classes having interpretation in coloured trees of bounded height. We also introduce a common extension of cographs and of graphs with bounded shrub-depth -- m-partite cographs (still of bounded clique-width), which are well quasi-ordered by the relation "is an induced subgraph of" and therefore allow polynomial time testing of hereditary properties.