A prominent approach to implementing ontology-mediated queries (OMQs) is to rewrite into a first-order query, which is then executed using a conventional SQL database system. We consider the case where the ontology is formulated in the description logic EL and the actual query is a conjunctive query and show that rewritings of such OMQs can be efficiently computed in practice, in a sound and complete way. Our approach combines a reduction with a decomposed backwards chaining algorithm for OMQs that are based on the simpler atomic queries, also illuminating the relationship between first-order rewritings of OMQs based on conjunctive and on atomic queries. Experiments with real-world ontologies show promising results.
@article{arxiv.1804.06907,
title = {Computing FO-Rewritings in EL in Practice: from Atomic to Conjunctive Queries},
author = {Peter Hansen and Carsten Lutz},
journal= {arXiv preprint arXiv:1804.06907},
year = {2018}
}