Modal Fragments

Fuente: arXiv
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Main Authors: Bezhanishvili, Nick, Cate, Balder ten, Ganguly, Arunavo, Meier, Arne
Format: Preprint
Published: 2026
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author Bezhanishvili, Nick
Cate, Balder ten
Ganguly, Arunavo
Meier, Arne
author_facet Bezhanishvili, Nick
Cate, Balder ten
Ganguly, Arunavo
Meier, Arne
contents We survey systematic approaches to basis-restricted fragments of propositional logic and modal logics, with an emphasis on how expressive power and computational complexity depend on the allowed operators. The propositional case is well-established and serves as a conceptual template: Post's lattice organizes fragments via Boolean clones and supports complexity classifications for standard reasoning tasks. For modal fragments, we then bring together two historically independent lines of investigation: a general framework where modal fragments are parameterized by a basis of "connectives" defined by arbitrary modal formulas (initially proposed and studied by logicians such as Kuznetsov and Ratsa in the 1970s), and the more tractable class of what we call simple modal fragments parameterized by Boolean functions plus selected modal operators, where Post-lattice methods enable systematic decidability and dichotomy results. Along the way, we collect and extend results on teachability and exact learnability from examples for both propositional fragments and simple modal fragments, and we conclude by identifying several open problems.
format Preprint
id arxiv_https___arxiv_org_abs_2603_05055
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Modal Fragments
Bezhanishvili, Nick
Cate, Balder ten
Ganguly, Arunavo
Meier, Arne
Logic in Computer Science
Logic
We survey systematic approaches to basis-restricted fragments of propositional logic and modal logics, with an emphasis on how expressive power and computational complexity depend on the allowed operators. The propositional case is well-established and serves as a conceptual template: Post's lattice organizes fragments via Boolean clones and supports complexity classifications for standard reasoning tasks. For modal fragments, we then bring together two historically independent lines of investigation: a general framework where modal fragments are parameterized by a basis of "connectives" defined by arbitrary modal formulas (initially proposed and studied by logicians such as Kuznetsov and Ratsa in the 1970s), and the more tractable class of what we call simple modal fragments parameterized by Boolean functions plus selected modal operators, where Post-lattice methods enable systematic decidability and dichotomy results. Along the way, we collect and extend results on teachability and exact learnability from examples for both propositional fragments and simple modal fragments, and we conclude by identifying several open problems.
title Modal Fragments
topic Logic in Computer Science
Logic
url https://arxiv.org/abs/2603.05055