A type of IVOA resource describing (exactly) one database independently of any service giving access to the database. The mandatory core of the element details the database itself. There may, optionally, be additional elements describing the provenance and astronomical usage of the resource. The structure of the database. There may be detailed metadata for zero or more tables, and these are intended to be read by software. The must also be a human-readable description and a name. A db:DB element with no tables could be used to register a database for which the detailed schemata have not yet been worked out.