Abstract Information systems have to deal with an increasing amount of data that is
heterogeneous, unstructured, or incomplete. In order to align and complete data, systems …

Recent years have seen an increasing interest in ontology-mediated query answering, in
which the semantic knowledge provided by an ontology is exploited when querying data …

This chapter considers the notion of a formal ontology, which is a conceptual vocabulary
equipped with a logical semantics. Three families of knowledge representation and …

Combined approaches have become a successful technique for solving conjunctive query
(CQ) answering over description logics (DL) ontologies. Nevertheless, existing approaches …

In ontology-mediated querying, description logic (DL) ontologies are used to enrich
incomplete data with domain knowledge which results in more complete answers to queries …

Conjunctive Query (CQ) answering is a primary reasoning task over knowledge bases.
However, when considering expressive description logics, query answering can be …

We consider the problem of ontological query answering, that is, the problem of answering a
database query (typically a conjunctive query) in the presence of an ontology. This means …

Nominal schemas have been proposed as an extension to Description Logics (DL), the
knowledge representation paradigm underlying the Web Ontology Language (OWL). They …

The disjunctive skolem chase is a sound and complete (albeit non-terminating) algorithm
that can be used to solve conjunctive query answering over DL ontologies and programs …

Recently, it has been shown that ontologies with large datasets can be efficiently
materialized by a so-called abstraction refinement technique. The technique consists of the …