Compiling and running in Windows

I am trying to integrate gprolog with other languages such as Java
to create the GUI front end. How is it best to do this? Is it possible
to compile my prolog program using gplc (in windows with nasm) so that
the executable reads some data (prolog facts) from another file and does
some processing and outputs the result into standard output?

I have this program(a.pl):

initialization(allfacts(L)).
fact(a).
fact(b).
allfacts(L):-
     bagof(fact(A),fact(A),L).

after doing "gplc a.pl" it created a.exe. First of all, I got a warning
saying "warning: singleton variables [L] for initialization/1",could you
tell me what does this mean? Secondly, when I run a.exe, it opened a
prolog prompt and did not automatically execute
initialization(allfacts(L)). Is it possible so that when I run a.exe, it
does not go into a prolog prompt and just executes "allfacts" and prints
the result to the screen?

Thank you Daniel :)

Anthony