Mapping Relational Databases into Ontologies through a Graph-based Formal Model

One of key issues of the Semantic Web applications is the lack of semantic data (ontologies). Although the vast majority of data are stored in the popular relational databases, they are still not easily available for many next generation Web applications. Therefore, one of core challenges of Semantic Web is whether these applications can automatically retrieve semantic information from the existed relational databases. This paper proposes a middle graph-based formal model language, W-graph, a bridge between relational databases and ontologies, which abstracts semantic information from relational database instances semi-automatically and then generates an OWL ontology automatically. This method not only maps relational database schemata to ontologies, but also populates ontologies with data stored in databases. Moreover, a proof of semantic preserving on the mapping is provided, and a case study and an implemented prototype tool are also reported.