A Horn extension of DL-Lite with NL data complexity

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Hauptverfasser: Arpasi, Janos, Bednarczyk, Bartosz Jan, Ortiz, Magdalena
Format: Preprint
Veröffentlicht: 2026
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author Arpasi, Janos
Bednarczyk, Bartosz Jan
Ortiz, Magdalena
author_facet Arpasi, Janos
Bednarczyk, Bartosz Jan
Ortiz, Magdalena
contents The literature on ontology-mediated query answering (OMQA) has been shaped by two key results: first-order rewritability for DL-Lite, and PTime-hardness of data complexity for essentially every description logic beyond it. This has effectively positioned DL-Lite as the only practical choice for query rewriting, restricting OMQA solutions to first-order queries and ontologies that can be rewritten into them. This AC0 vs. PTime dichotomy is especially limiting if we consider that OMQA targets graph-structured data, and that standard graph query languages (including the recent ISO standards GQL and SQL/PGQ) are typically NL-complete. Towards identifying a rich Horn DL that can be rewritten into graph query languages and that can still express many ELI and DL-Lite ontologies, we introduce a stratification mechanism for ELI that controls the interaction between conjunction and recursion. In this way, we obtain ELbotpreceq, a description logic that strictly extends the core DL-Lite, supports reachability axioms and restricted conjunction, and allows for reasoning in NL. We establish the NL upper bound via a rewriting into nested two-way regular path queries, a fragment of GQL, providing initial evidence that our ontology language is a promising candidate for extending OMQA to graph query languages.
format Preprint
id arxiv_https___arxiv_org_abs_2605_13367
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A Horn extension of DL-Lite with NL data complexity
Arpasi, Janos
Bednarczyk, Bartosz Jan
Ortiz, Magdalena
Logic in Computer Science
Artificial Intelligence
Databases
The literature on ontology-mediated query answering (OMQA) has been shaped by two key results: first-order rewritability for DL-Lite, and PTime-hardness of data complexity for essentially every description logic beyond it. This has effectively positioned DL-Lite as the only practical choice for query rewriting, restricting OMQA solutions to first-order queries and ontologies that can be rewritten into them. This AC0 vs. PTime dichotomy is especially limiting if we consider that OMQA targets graph-structured data, and that standard graph query languages (including the recent ISO standards GQL and SQL/PGQ) are typically NL-complete. Towards identifying a rich Horn DL that can be rewritten into graph query languages and that can still express many ELI and DL-Lite ontologies, we introduce a stratification mechanism for ELI that controls the interaction between conjunction and recursion. In this way, we obtain ELbotpreceq, a description logic that strictly extends the core DL-Lite, supports reachability axioms and restricted conjunction, and allows for reasoning in NL. We establish the NL upper bound via a rewriting into nested two-way regular path queries, a fragment of GQL, providing initial evidence that our ontology language is a promising candidate for extending OMQA to graph query languages.
title A Horn extension of DL-Lite with NL data complexity
topic Logic in Computer Science
Artificial Intelligence
Databases
url https://arxiv.org/abs/2605.13367