Explanations for ontology-mediated query answers

Ontology-mediated query answering is a paradigm that seeks to exploit the semantic knowledge expressed in terms of ontologies to improve query answers over incomplete data sources. In this thesis, we consider explanations for ontology-mediated query answers under the classical semantics. We provide a comprehensive complexity analysis of a wide range of computational problems, associated with explaining ontology-mediated query answers. We study explanations both for positive and negative ontology-mediated query answers under different minimality criteria, both for existential rules and description logics. This allows us to indicate similarities and point out differences in the complexity of explaining ontology-mediated query answers for these different settings.