Some old Prologs used to have consult/1 that simply added the clauses to the database and reconsult/1 to reload during development. It lead to a lot of confusion. SWI-Prolog always wipes clauses loaded from a file that was already loaded. If you wish to load clauses from different files you need the ISO standard :- multifile Name/Arity ... directive; see multifile/1.

See also

- For reloading files after editing, use make/0.

- For more info on sourcecode management, see Initialising and Managing a Prolog project from the SWI-Prolog reference manual.