Conservative Extensions in Guarded and Two-Variable Fragments

Authors Jean Christoph Jung, Carsten Lutz, Mauricio Martel, Thomas Schneider, Frank Wolter

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Jean Christoph Jung
Carsten Lutz
Mauricio Martel
Thomas Schneider
Frank Wolter

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Jean Christoph Jung, Carsten Lutz, Mauricio Martel, Thomas Schneider, and Frank Wolter. Conservative Extensions in Guarded and Two-Variable Fragments. In 44th International Colloquium on Automata, Languages, and Programming (ICALP 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 80, pp. 108:1-108:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)


We investigate the decidability and computational complexity of (deductive) conservative extensions in fragments of first-order logic (FO), with a focus on the two-variable fragment FO2 and the guarded fragment GF. We prove that conservative extensions are undecidable in any FO fragment that contains FO2 or GF (even the three-variable fragment thereof), and that they are decidable and 2ExpTime-complete in the intersection GF2 of FO2 and GF.
  • Conservative Extensions
  • Decidable Fragments of First-Order Logic
  • Computational Complexity}


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