Year: 2024
Type: conference-paper
Abstract: Ontology-based query answering is a problem that takes as input a set of facts F, an ontology R (typically expressed by existential rules), a Boolean query q , and asks whether R and F entails q. This problem is undecidable in general, and a widely investigated approach to tackle it is called query rewriting: from (R,q) (a ``rule query'') is computed q_R such that for any set of facts F, it holds that R and F entail q iff F entails q_R. The literature mostly focused on q_R expressed as a union of conjunctive queries (UCQs), and an algorithm that such a q_R whenever it exists has been proposed in the literature. However, UCQ-rewritability is applicable only in restricted settings. This raises the question whether such a generic algorithm can be designed for a more expressive language, such as datalog. We solve this question by the negative, by studying the difference between datalog-expressibility and datalog-rewritability. In particular, we show that query answering under datalog-expressible rule queries is undecidable.
DOI: 10.24963/kr.2024/22
Authors: David Carral, Lucas Larroque, Michaël Thomazo
Institutions: Centre National de la Recherche Scientifique, Institut national de recherche en sciences et technologies du numérique, Université de Montpellier, Laboratoire d'Informatique, de Robotique et de Microélectronique de Montpellier, Université Paris Sciences et Lettres, École Normale Supérieure - PSL, Département d'Informatique
Language: English
Topic: Semantic Web and Ontologies
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: gold
OpenAlex ID: W4402953426