Ontology for Relational Database Metadata

Dear LOD community,

we're currently looking for an ontology to describe relational database metadata. In the D2RQ vocabulary and in the R2RML standard, there are some simple concepts for representing databases and tables, yet what we're looking for goes far beyond what can be expressed with these vocabularies: we are looking for a schema allowing us to describe the internal structure of relational databases, including database meta information (database type, version number, ...), table names, attributes and associated datatypes, key and foreign key relationships, indizes, and the like.

If anyone is aware of ontologies covering this subject, we would be glad to get some pointers.

Best regards,
Michael Schmidt