A Data Complexity and Rewritability Tetrachotomy of Ontology-Mediated Queries with a Covering Axiom
- Computational aspects of knowledge representation-General
- Description logics-General
- Ontology-based data access, integration, and exchange-General
Aiming to understand the data complexity of answering conjunctive queries mediated by an axiom stating that a class is covered by the union of two other classes, we show that deciding their first-order rewritability is PSPACE-hard and obtain a number of sufficient conditions for membership in AC0, L, NL, and P. Our main result is a complete syntactic AC0/NL/P/CONP tetrachotomy of path queries under the assumption that the covering classes are disjoint.