This method actually opens a connection to the database.

Any data specific to the connection (such as a database handle created by the database API when opening the connection) must be stored in a private structure (which should be defined in the gda-<providername>.h file as a <Providername>ConnectionData); this private structure's adress should be "attached" to the GdaConnection object using the gda_connection_internal_set_provider_data().

This method actually closes a connection previously opened by the open_connection() virtual method. This method is not mandatory for virtual providers.

The connection specific data for the database API can be retrieved using the gda_connection_internal_get_provider_data() method.

This method returns the name of the database to which a connection is opened.