---
title: "Combining Existential Rules with the Power of CP-Theories"
authors:
  - "Tommaso Di Noia"
  - "Thomas Lukasiewicz"
  - "Maria Vanina Martinez"
  - "Gerardo Ignacio Simari"
  - "Oana Tifrea-Marciuska"
doi: ""
url: "https://ijcai.org/proceedings/2015/413"
pdf: "https://ijcai.org/proceedings/2015/0413.pdf"
venue: "Proceedings of the Twenty-Fourth International Joint Conference on Artificial Intelligence"
year: 2015
pages: "2918-2924"
track: "Special Track on Knowledge Representation and Reasoning"
keywords:
---

# Combining Existential Rules with the Power of CP-Theories

Tommaso Di Noia, Thomas Lukasiewicz, Maria Vanina Martinez, Gerardo Ignacio Simari, Oana Tifrea-Marciuska

*Proceedings of the Twenty-Fourth International Joint Conference on Artificial Intelligence*, pages 2918-2924.

## Abstract

The tastes of a user can be represented in a natural way by using qualitative preferences. In this paper, we explore how ontological knowledge expressed via existential rules can be combined with CP-theories to (i) represent qualitative preferences along with domain knowledge, and (ii) perform preference-based answering of conjunctive queries (CQs). We call these combinations ontological CP-theories (OCP-theories). We define skyline and k-rank answers to CQs based on the user’s preferences encoded in an OCP-theory, and provide an algorithm for computing them. We also provide precise complexity (including data tractability) results for deciding consistency, dominance, and CQ skyline membership for OCP-theories.