,
Santiago Guzmán-Pro
Creative Commons Attribution 4.0 International license
Many computational problems can be modelled as the class of all finite structures A that satisfy a fixed first-order sentence ϕ hereditarily, i.e., we require that every (induced) substructure of A satisfies ϕ. We call the corresponding computational problem the hereditary model checking problem for ϕ, and denote it by Her(ϕ). We present a complete description of the quantifier prefixes for ϕ such that Her(ϕ) is in P; we show that for every other quantifier prefix there exists a formula ϕ with this prefix such that Her(ϕ) is coNP-complete. Specifically, we show that if Q is of the form ∀*∃∀* or of the form ∀*∃*, then Her(ϕ) can be solved in polynomial time whenever the quantifier prefix of ϕ is Q. Otherwise, Q contains ∃∃∀ or ∃∀∃ as a subword, and in this case, there is a first-order formula ϕ whose quantifier prefix is Q and Her(ϕ) is coNP-complete. Moreover, we show that there is no algorithm that decides for a given first-order formula ϕ whether Her(ϕ) is in P (unless P=NP).
@InProceedings{bodirsky_et_al:LIPIcs.CSL.2026.6,
author = {Bodirsky, Manuel and Guzm\'{a}n-Pro, Santiago},
title = {{Hereditary First-Order Logic: the Tractable Quantifier Prefix Classes}},
booktitle = {34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
pages = {6:1--6:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-411-6},
ISSN = {1868-8969},
year = {2026},
volume = {363},
editor = {Guerrini, Stefano and K\"{o}nig, Barbara},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2026.6},
URN = {urn:nbn:de:0030-drops-254308},
doi = {10.4230/LIPIcs.CSL.2026.6},
annote = {Keywords: Quantifier prefix, first-order Logic, Computational Complexity, Polynomial-time algorithm, coNP-completeness}
}