Julien,

A Feature Request for a Boolean datatype has been recorded for the
Firebird project (quite some time ago).

One of the main constraints to the new datatype, is that its
implementation would require a new ODS (On Disk Structure) in addition
to the changes to the engine logic.

Another 'constraint' is the fact that a lot of people consider the
DOMAIN and database access tools solutions (IBO/BDE as Boolean) to be an
adequate solution. Accordingly, there isn't a lot of 'buy-in' for
developers to invest their efforts.

--

Sean Leyne
There is nothing wrong with Interbase
that Firebird can't fix
http://FirebirdSQL.org