Regular Expressions for Tree-Width 2 Graphs

Author Amina Doumane

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Amina Doumane
  • CNRS, LIP, ENS Lyon, France


I want to thank Denis Kuperberg for helpful discussions on the content and presentation.

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Amina Doumane. Regular Expressions for Tree-Width 2 Graphs. In 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 229, pp. 121:1-121:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


We propose a syntax of regular expressions, which describes languages of tree-width 2 graphs. We show that these languages correspond exactly to those languages of tree-width 2 graphs, definable in the counting monadic second-order logic (CMSO).

Subject Classification

ACM Subject Classification
  • Mathematics of computing → Discrete mathematics
  • Tree width
  • MSO
  • Regular expressions


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