]> An Ontology to describe the schema information of a relational database. Database The class of databases. Table The class of database tables. Column The class of database columns. PrimaryKey The Primary Key of a Table. has A Thing may have other things inside. hasTable A Database has a set of Tables. hasColumn A Table has a set of Columns. 1 isIdentifiedBy A Table is identified by a Primary Key references A Foreign Key Column references another Column. length The maximum length, an entry of the Column may have. scale The scale an entry of the Column has, e.g. of a decimal value.