% Define parent-child relationships
parent(alice, bob).

% Define a rule to perform unification
unify_predicate(Y) :-
    parent(alice, bob),      % First predicate
    parent(alice, Y).        % Second predicate with a variable

% Main function to perform the query and print the result
main :-
    unify_predicate(Y),
    write('Unify Y = '), write(Y), nl.

% Test case for unification
test_unification :-
    main.

% Test case for failure when parent/3 is used
test_failure :-
    \+ (parent(alice, _, _) ; parent(_, _, alice)),
    write('Unification failed'), nl.

% Initialization directive for the unification test case
:- initialization(test_unification).

% Initialization directive for the failure test case
:- initialization(test_failure).