Symmetric Linear Arc Monadic Datalog and Gadget Reductions

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Hauptverfasser: Bodirsky, Manuel, Starke, Florian
Format: Preprint
Veröffentlicht: 2024
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author Bodirsky, Manuel
Starke, Florian
author_facet Bodirsky, Manuel
Starke, Florian
contents A Datalog program solves a constraint satisfaction problem (CSP) if and only if it derives the goal predicate precisely on the unsatisfiable instances of the CSP. There are three Datalog fragments that are particularly important for finite-domain constraint satisfaction: arc monadic Datalog, linear Datalog, and symmetric linear Datalog, each having good computational properties. We consider the fragment of Datalog where we impose all of these restrictions simultaneously, i.e., we study \emph{symmetric linear arc monadic (slam) Datalog}. We characterise the CSPs that can be solved by a slam Datalog program as those that have a gadget reduction to a particular Boolean constraint satisfaction problem. We also present exact characterisations in terms of a homomorphism duality (which we call \emph{unfolded caterpillar duality}), and in universal-algebraic terms (using known minor conditions, namely the existence of quasi Maltsev operations and $k$-absorptive operations of arity $nk$}, for all $n,k \geq 1$). Our characterisations also imply that the question whether a given finite-domain CSP can be expressed by a slam Datalog program is decidable.
format Preprint
id arxiv_https___arxiv_org_abs_2407_04924
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Symmetric Linear Arc Monadic Datalog and Gadget Reductions
Bodirsky, Manuel
Starke, Florian
Rings and Algebras
Computational Complexity
Logic in Computer Science
A Datalog program solves a constraint satisfaction problem (CSP) if and only if it derives the goal predicate precisely on the unsatisfiable instances of the CSP. There are three Datalog fragments that are particularly important for finite-domain constraint satisfaction: arc monadic Datalog, linear Datalog, and symmetric linear Datalog, each having good computational properties. We consider the fragment of Datalog where we impose all of these restrictions simultaneously, i.e., we study \emph{symmetric linear arc monadic (slam) Datalog}. We characterise the CSPs that can be solved by a slam Datalog program as those that have a gadget reduction to a particular Boolean constraint satisfaction problem. We also present exact characterisations in terms of a homomorphism duality (which we call \emph{unfolded caterpillar duality}), and in universal-algebraic terms (using known minor conditions, namely the existence of quasi Maltsev operations and $k$-absorptive operations of arity $nk$}, for all $n,k \geq 1$). Our characterisations also imply that the question whether a given finite-domain CSP can be expressed by a slam Datalog program is decidable.
title Symmetric Linear Arc Monadic Datalog and Gadget Reductions
topic Rings and Algebras
Computational Complexity
Logic in Computer Science
url https://arxiv.org/abs/2407.04924