We present the framework of ontology-based data access, a semantic paradigm for
providing a convenient and user-friendly access to data repositories, which has been …

The chase algorithm is a fundamental tool for query evaluation and for testing query
containment under tuple-generating dependencies (TGDs) and equality-generating …

In this paper we study data complexity of answering conjunctive queries over description
logic (DL) knowledge bases constituted by a TBox and an ABox. In particular, we are …

Answering conjunctive queries (CQs) over a set of facts extended with existential rules is a
prominent problem in knowledge representation and databases. This problem can be …

Ontological queries are evaluated against a knowledge base consisting of an extensional
database and an ontology (ie, a set of logical assertions and constraints that derive new …

The need for an ontological layer on top of data, associated with advanced reasoning
mechanisms able to exploit ontological knowledge, has been acknowledged in the …

We address the issue of Ontology-Based Data Access, with ontologies represented in the
framework of existential rules, also known as Datalog±. A well-known approach involves …

We perform an in-depth complexity analysis of query answering under guarded-based
classes of disjunctive tuple-generating dependencies (DTGDs), focusing on (unions of) …

Large-scale knowledge graphs (KGs) are widely used in industry and academia, and
provide excellent use-cases for ontologies. We find, however, that popular ontology …

The chase has become a staple of modern database theory with applications in data
integration, query optimisation, data exchange, ontology-based query answering, and many …