| Did you know ... | Search Documentation: | 
| Reading dynamic data from a file | 
It may seem attractive to use consult/1 for loading a file holding `case data' as Prolog facts. However, this is not a very good plan.
A much better approach is to load the file by hand. If we have dynamic data on a graph as arc/2 facts, this looks as follows.
:- use_module(library(error)).
:- dynamic arc/2.
load_arcs(File) :-
        retractall(arc(_,_)),
        setup_call_cleanup(
            open(File, read, Stream),
            load_arcs_from_stream(Stream),
            close(Stream)).
load_arcs_from_stream(Stream) :-
        read(Stream, T0),
        load_arcs(T0, Stream).
load_arcs(end_of_file, _) :- !.
load_arcs(arc(From, To), Stream) :- !,
        assert(arc(From, To)),
        read(Stream, T2),
        load_arcs(T2, Stream).
load_arcs(Term, _Stream) :-
        type_error(arc, Term).
Of course you should adapt this code to your case. This code properly handles your code as dynamic data and doesn't allow a user of your program to fool you by adding a term
arc(_, _) :- shell('format C').