libgda offers a special XML file format intended to represent the whole structure of a data source's structure. This file format is used to import/export data to/from a given data source. It is also used by the (non-existant yet) XML provider, which simulates a database system by using the data stored in one of these files.
The gda-common library includes a class, called Gda_XmlDatabase, which offers a way for programatically read and modify one of these XML files.