Mapping Data to Ontologies with Exceptions Using Answer Set Programming

In ontology-based data access, databases are connected to an ontology via mappings from queries over the database to queries over the ontology. In this paper, we consider mappings from relational databases to first-order ontologies, and define an ASP-based framework for GLAV mappings with queries over the ontology in the mapping rule bodies. We show that this type of mappings can be used to express constraints and exceptions, as well as being a powerful mechanism for succinctly representing OBDA mappings. We give an algorithm for brave reasoning in this setting, and show that this problem has either the same data complexity as ASP (NP- complete), or it is at least as hard as the complexity of checking entailment for the ontology queries. Furthermore, we show that for ontologies with UCQ-rewritable queries there exists a natural reduction from mapping programs to \exists-ASP, an extension of ASP with existential variables that itself admits a natural reduction to ASP.