Automatic mapping rules and OWL ontology extraction for the OBDA Ontop

Extracting Ontop mapping rules and OWL ontology manually from a relational schema is a tedious task. We present an automatic approach for extracting Ontop mappings and OWL ontology from an existing database schema. The end users can access the underlying data source through SPARQL queries. A SPARQL query is written according to the extracted ontology and the end user does not need to know about the underlying data source and its schema. The proposed approach takes into consideration the different relationships between entities of the database schema. Instead of extracting a flat ontology that is an exact copy of the database schema, it extracts a rich ontology. The extracted ontology can also be used as an intermediate between a domain ontology and the underlying database schema. The experiment results indicate that the extracted mappings and ontology are accurate. i.e., end users can query all data (using SPARQL) from the underlying database source in the same way as if they have written SQL queries.