Computing FO-Rewritings in EL in Practice: from Atomic to Conjunctive Queries
This work addresses the implementation challenge of ontology-mediated queries for database systems, though it appears incremental as it builds on existing methods for atomic queries.
The paper tackled the problem of efficiently computing first-order rewritings for ontology-mediated queries in description logic EL with conjunctive queries, achieving practical performance with sound and complete results, as shown in experiments with real-world ontologies.
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.