Answering Counting Queries over DL-Lite Ontologies

TL;DR

This paper explores the complexity of answering counting queries over DL-Lite ontologies, introducing a general form of counting query and analyzing its computational properties under various restrictions.

Contribution

It introduces a general form of counting query in the context of DL-Lite ontologies and studies its complexity, providing new insights and bounds for practical restrictions.

Findings

Answering counting queries is generally intractable.

Certain restrictions lead to improved complexity bounds.

The paper relates new counting queries to existing query frameworks.

Abstract

Ontology-mediated query answering (OMQA) is a promising approach to data access and integration that has been actively studied in the knowledge representation and database communities for more than a decade. The vast majority of work on OMQA focuses on conjunctive queries, whereas more expressive queries that feature counting or other forms of aggregation remain largely unex-plored. In this paper, we introduce a general form of counting query, relate it to previous proposals, and study the complexity of answering such queries in the presence of DL-Lite ontologies. As it follows from existing work that query answering is intractable and often of high complexity, we consider some practically relevant restrictions, for which we establish improved complexity bounds.