RSAComb: Combined Approach for CQ Answering in RSA

The combined approach is a well-known technique used to address the problem of conjunctive query (CQ) answering over knowledge bases. Various versions of the approach exist for relevant fragments of OWL 2. In this paper we focus on the combined approach for CQ answering over RSA, a class of ontologies that extends the OWL 2 profiles while maintaining the tractability of standard reasoning tasks. The algorithm was first presented in [4], but to the best of our knowledge a stable implementation is not currently available. We present RSAComb, a novel implementation of the algorithm that introduces several improvements and fixes to the original approach and uses RDFox as the underlying Datalog reasoner. As well as providing high performance, the extended features of RDFox allow for an optimised implementation of the filtration step. We developed the system with modularity and stability in mind so that it can be used as a standalone tool or integrated into other software as a library. We include an extensive evaluation of the system, focusing on performance and scalability.