The database frame uses the same execution flow as the client frame.
Except that we ex-changed the Prolog agent for the Prolog driver.
Again there is not much to say about the im-plementation of the
database frame. It mirrors the implementation of the client frame.
The Java class has only a different name, but the repertoire of the
methods is the same. The sole differ-ence is that that we consult
the Prolog driver instead of the Prolog agent.