Comparing query answering in OBDA tools over W3C-compliant specifications

The Ontology-Based Data Access (OBDA) paradigm aims at providing to the users a unified and shared conceptual view of the domain of interest (ontology), while still enabling the data to be stored in different data sources. Such data are mapped to the ontology through declarative specifications. In this work we consider the ontology expressed in OWL 2 QL, relational sources, the mapping expressed in R2RML, and the user queries expressed in SPARQL. In this W3C-compliant setting, we compare query answering in the two main tools for OBDA, namely, Mastro and Ontop, by resorting to the NPD Benchmark, and the full-fledged OBDA application developed for the Italian Automobile Club (ACI). We also discuss how R2RML support is added to Mastro.