---
title: "Expressive Completeness of Existential Rule Languages for Ontology-Based Query Answering"
authors:
  - "Heng Zhang"
  - "Yan Zhang"
  - "Jia-Huai You"
doi: ""
url: "https://ijcai.org/proceedings/2016/192"
pdf: "https://ijcai.org/proceedings/2016/0192.pdf"
venue: "Proceedings of the Twenty-Fifth International Joint Conference on Artificial Intelligence"
year: 2016
pages: "1330-1336"
track: ""
keywords:
---

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

Heng Zhang, Yan Zhang, Jia-Huai You

*Proceedings of the Twenty-Fifth International Joint Conference on Artificial Intelligence*, pages 1330-1336.

## Abstract

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.