---
title: "Intensional and Extensional Views in DL-Lite Ontologies"
authors:
  - "Marco Console"
  - "Giuseppe De Giacomo"
  - "Maurizio Lenzerini"
  - "Manuel Namici"
doi: "10.24963/ijcai.2021/251"
url: "https://ijcai.org/proceedings/2021/251"
pdf: "https://ijcai.org/proceedings/2021/0251.pdf"
venue: "Proceedings of the Thirtieth International Joint Conference on Artificial Intelligence"
year: 2021
pages: "1822-1828"
track: "Main Track"
keywords:
  - "Knowledge Representation and Reasoning: Description Logics and Ontologies"
  - "Knowledge Representation and Reasoning: Knowledge Representation Languages"
  - "Knowledge Representation and Reasoning: Reasoning about Knowledge and Belief"
---

# Intensional and Extensional Views in DL-Lite Ontologies

Marco Console, Giuseppe De Giacomo, Maurizio Lenzerini, Manuel Namici

*Proceedings of the Thirtieth International Joint Conference on Artificial Intelligence*, pages 1822-1828. DOI: [10.24963/ijcai.2021/251](https://doi.org/10.24963/ijcai.2021/251)

## Abstract

The use of virtual collections of data is often essential in several
data and knowledge management tasks. In the literature, the standard
way to define virtual data collections is via views, i.e., virtual
relations defined using queries.  In data and knowledge bases, the
notion of views is a staple of data access, data integration and
exchange, query optimization, and data privacy.  In this work, we
study views in Ontology-Based Data Access (OBDA) systems.
OBDA is a powerful paradigm for accessing data through an
ontology, i.e., a conceptual specification of the domain of interest
written using logical axioms. Intuitively, users of an OBDA system
interact with the data only through the ontology's conceptual lens. We
present a novel framework to express natural and sophisticated forms
of views in OBDA systems and introduce fundamental reasoning tasks for
these views. We study the computational complexity of these tasks and
present classes of views for which these tasks are tractable or at
least decidable.