The idea is to defined the schema of database in XML instead of SQL. The XML is provided with a DTD in order to:
1. validate xml that you write to see if it is indeed a dbdef.
2. help author the xml (various xml writers can use the DTD to help you write the xml).
Documentation of the XML format is provided (auto generated from the DTD).

The XML format itself is database agnostic. Dbdef has a backend per database (and new backends can even be added by a USER) which translates the XML into SQL for a specific database server/server version (server version is taken into consideration since, for instance, Oracle 8 can have different features or syntax from Oracle 9).

Currently implemented backends are Mysql, Posgresql, Oracle.

Other databases which are on our list in alphabetic order) are:
ADO Adabas Altera AnyData CSV DB2 DBM DtfSQLmac Empress EmpressNet Excel File Fulcrum Illustra Informix Informix4 Ingres InterBase JDBC LDAP MaxDB Multiplex ODBC Oracle PrimeBase RAM Redbase SQLRelay SQLite SQLite2 Solid Sybase XBase iPod mSQL.