Ontology Evolution in Data Integration: Query Rewriting to the Rescue

The evolution of ontologies is an undisputed necessity in ontology-based data integration. In such systems ontologies are used as global schema in order to formulate queries that are answered by the data integration systems. Yet, few research efforts have focused on addressing the need to reflect ontology evolution onto the underlying data integration systems. In most of these systems, when ontologies change their relations with the data sources, i.e., the mappings, are recreated manually, a process which is known to be error-prone and time-consuming. In this paper, we provide a solution that allows query answering under evolving ontologies without mapping redefinition. To achieve that, query rewriting techniques are exploited in order to produce equivalent rewritings among ontology versions. Whenever equivalent rewritings cannot be produced we a) guide query redefinition or b) provide the best "over-approximations". We show that our approach can greatly reduce human effort spent since continuous mapping redefinition on evolving ontologies is no longer necessary.