Compact Query Rewritings for Ontology-Based Query Answering

Michaël Thomazo

Abstract: Ontology-based query answering is an important reasoning problem at the core of logic-based data integration. Formally, the problem takes as input a database instance \(I\), a set of existential rules \(\mathcal {R}\), and a Boolean conjunctive query \(q\), and asks whether \(I, \mathcal {R}\models q\). The query entailment problem thus defined is usually reduced towards a query evaluation problem, either through materialization of entailed atoms, or through query rewriting. In these lecture notes, we present a couple of query rewriting algorithms, and discuss an approach whose aim is to avoid a blow-up in the size of the rewritings in cases that are typically present in real-world, namely in the presence of (large) role and concepts hierarchies.