Capturing Homomorphism-Closed Decidable Queries with Existential Rules
Logic in Computer Science
2021-07-19 v1 Databases
Abstract
Existential rules are a very popular ontology-mediated query language for which the chase represents a generic computational approach for query answering. It is straightforward that existential rule queries exhibiting chase termination are decidable and can only recognize properties that are preserved under homomorphisms. In this paper, we show the converse: every decidable query that is closed under homomorphism can be expressed by an existential rule set for which the standard chase universally terminates. Membership in this fragment is not decidable, but we show via a diagonalisation argument that this is unavoidable.
Cite
@article{arxiv.2107.07811,
title = {Capturing Homomorphism-Closed Decidable Queries with Existential Rules},
author = {Camille Bourgaux and David Carral and Markus Krötzsch and Sebastian Rudolph and Michaël Thomazo},
journal= {arXiv preprint arXiv:2107.07811},
year = {2021}
}
Comments
Technical Report of our KR 2021 Paper