,
Sharon Shoham
Creative Commons Attribution 4.0 International license
Recently, symbolic structures were proposed as finite representations of potentially infinite first-order structures, where Linear Integer Arithmetic terms and formulas define the domain and interpretations of a structure. We generalize symbolic structures to use any base theory that admits a standard model. Symbolic structures induce a symbolic model property, which holds for a fragment of first-order logic if every satisfiable formula in the fragment has a symbolic model. The symbolic model property implies decidability, since the model-checking problem for symbolic structures is decidable. We use the symbolic model property to prove decidability for several fragments that extend the fragment of stratified formulas, relaxing the quantifier-alternation constraints by allowing one sort to have self-looping functions, under certain restrictions. To establish the symbolic model property for these fragments we construct a symbolic model for a formula from an arbitrary model. The construction and its correctness are proved in a generic fashion, which may be instantiated to other similarly restricted fragments.
@InProceedings{elad_et_al:LIPIcs.LICS.2026.40,
author = {Elad, Neta and Shoham, Sharon},
title = {{Decidability Results for Fragments of First-Order Logic via a Symbolic Model Property}},
booktitle = {41st Annual Symposium on Logic in Computer Science (LICS 2026)},
pages = {40:1--40:27},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-434-5},
ISSN = {1868-8969},
year = {2026},
volume = {380},
editor = {Faggian, Claudia and Katoen, Joost-Pieter},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.LICS.2026.40},
URN = {urn:nbn:de:0030-drops-268274},
doi = {10.4230/LIPIcs.LICS.2026.40},
annote = {Keywords: first-order logic, decidability, symbolic structures}
}