ACQuA is a hybrid query answering framework that combines black-box services to provide a CQ answering service for OWL. Specifically, it combines scalable CQ answering services for tractable languages with a CQ answering service for a more expressive language approaching the full OWL 2. If the query can be fully answered by one of the tractable services, then that service is used. Otherwise the tractable services are used to compute lower and upper bound approximations, taking the union of the lower bounds and the intersection of the upper bounds. If the bounds don't coincide, then the "gap" answers are checked using the "full" service.
This reference implementation combines RSAComb, PAGOdA, and HermiT, but these tools can be potentially substituted or augmented with more capable ones to improve the overall performance of the system.
This project has been released as free and open source software and licensed under the Apache License 2.0.