---
title: "EQL-Lite: Effective First-Order Query Processing in Description Logics"
authors:
  - "Diego Calvanese"
  - "Giuseppe De Giacomo"
  - "Domenico Lembo"
  - "Maurizio Lenzerini"
  - "Riccardo Rosati"
doi: ""
url: "https://ijcai.org/proceedings/2007/42"
pdf: "https://ijcai.org/proceedings/2007/0042.pdf"
venue: "Proceedings of the Twentieth International Joint Conference on Artificial Intelligence"
year: 2007
pages: "274-278"
track: ""
keywords:
---

# EQL-Lite: Effective First-Order Query Processing in Description Logics

Diego Calvanese, Giuseppe De Giacomo, Domenico Lembo, Maurizio Lenzerini, Riccardo Rosati

*Proceedings of the Twentieth International Joint Conference on Artificial Intelligence*, pages 274-278.

## Abstract

Querying Description Logic knowledge bases has received great attention in the last years. In such a problem, the need of coping with incomplete information is the distinguishing feature with respect to querying databases. Due to this feature, we have to deal with two conflicting needs: on the one hand, we would like to query the knowledge base with sophisticated mechanisms provided by full first-order logic (FOL); on the other hand, the presence of incomplete information makes query answering a much more difficult task than in databases. In this paper we advocate the use of a nonmonotonic epistemic FOL query language as a means for expressing sophisticated queries over Description Logic knowledge bases. We show that through a controlled use of the epistemic operator, resulting in the language called EQL-Lite, we are able to formulate full FOL queries over Description Logic knowledge bases, while keeping computational complexity of query answering under control. In particular, we show that EQL-Lite queries over DL-Lite knowledge bases are FOL reducible (i.e., compilable into SQL) and hence can be answered in LOGSPACE through standard database technologies.