Relational.OWL - A Data and Schema Representation Format Based on OWL "In this paper we introduce a Web Ontology Language (OWL)-based (Miller & Hendler 2004) representation format for relational data and schema components, which is particularly appropriate for exchanging items among remote database systems. OWL, originally created for the Semantic Web enables us to represent not only the data itself, but also its interpretation, i.e. knowledge about its format, its origin, its usage, or its original embedment in specific frameworks.
Hence, remote databases are instantly able to understand each other without having to arrange an explicit exchange format - the usage of OWL on both sides is sufficient. This would be impossible using present XML formats."
"Bizer introduced in (Bizer 2003) a mapping language between relational data and RDF, particularly between specific relational query results and RDF. Contrary to our approach, D2R MAP converts the stored data into ”real” RDF objects, i.e. an address would be represented as a RDF address ob ject. This approach takes into account, that the original database cannot be reconstructed using this kind of data representation anymore, since it does not contain information concerning the original schema of the database. As a result, the data represented with the D2R MAP language looses its relationship to the original database. Tracing the data to its original storage position is thus hardly possible."
Homepage, other papers (such as "Database to Semantic Web Mapping using RDF Query Languages" and the good "Bringing Relational Data into the Semantic Web using SPARQL and Relational.OWL") and documentation with beta versions of the software written in Java (uses Jena).
D2R Server 0.3 was release recently too.