# Expressive Completeness of Existential Rule Languages for Ontology-based Query Answering

arXiv: https://arxiv.org/abs/1604.05006 · HTML: https://mlsanity.com/paper/1604.05006/

## Key facts

- Cited by 2 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 18 Apr 2016.

## Built on by (most cited first, 2 of 2)

- [Characterizing the Program Expressive Power of Existential Rule Languages](https://mlsanity.com/paper/2112.08136/) (2021)
- [A Theory of Formalisms for Representing Knowledge](https://mlsanity.com/paper/2412.11855/) (2024)

## Abstract (arXiv)

Existential rules, also known as data dependencies in Databases, have been recently rediscovered as a promising family of languages for Ontology-based Query Answering. In this paper, we prove that disjunctive embedded dependencies exactly capture the class of recursively enumerable ontologies in Ontology-based Conjunctive Query Answering (OCQA). Our expressive completeness result does not rely on any built-in linear order on the database. To establish the expressive completeness, we introduce a novel semantic definition for OCQA ontologies. We also show that neither the class of disjunctive tuple-generating dependencies nor the class of embedded dependencies is expressively complete for recursively enumerable OCQA ontologies.