mutter_von(hilde, elsa).
vater_von(egon, elsa).
vater_von(paul, otto).
mutter_von(erna, otto).
mutter_von(elsa, gaby).
mutter_von(elsa, dieter).
vater_von(otto, gaby).
vater_von(otto, dieter).
geboren(otto, datum(1, april, 1960)).
grossvater_von(Grossvater, Enkel) :- vater_von(Grossvater, Vater),
                                     vater_von(Vater, Enkel).
grossvater_von(Grossvater, Enkel) :- vater_von(Grossvater, Mutter),
                                     mutter_von(Mutter, Enkel).
zwillinge(X, Y) :- geboren(X, T), geboren(Y, T),
                   mutter_von(M, X), mutter_von(M, Y).

?- vater_von(paul, dieter).
?- mutter_von(X, gaby).
?- grossvater_von(egon, Wer).
?- grossvater_von(Wer, dieter).
?- geboren(X, datum(1, april, _)).
?- geboren(X, datum(_, _, 1960)).
?- geboren(otto, Wann).
?- geboren(otto, datum(T, M, J)).
?- zwillinge(_, _).
?- geschwister(gaby, X).


---Ergebnis: ---------------------------------------------------------

?- vater_von(paul, dieter).

Resolution 1: No.


?- mutter_von(X{0}, gaby).

Resolution 1: Yes.
X = elsa

Resolution 2: No.


?- grossvater_von(egon, Wer{0}).

Resolution 1: Yes.
Wer = gaby

Resolution 2: Yes.
Wer = dieter

Resolution 3: No.


?- grossvater_von(Wer{0}, dieter).

Resolution 1: Yes.
Wer = paul

Resolution 2: Yes.
Wer = egon

Resolution 3: No.


?- geboren(X{0}, datum(1, april, _)).

Resolution 1: Yes.
X = otto

Resolution 2: No.


?- geboren(X{0}, datum(_, _, 1960)).

Resolution 1: Yes.
X = otto

Resolution 2: No.


?- geboren(otto, Wann{0}).

Resolution 1: Yes.
Wann = datum(1, april, 1960)

Resolution 2: No.


?- geboren(otto, datum(T{0}, M{0}, J{0})).

Resolution 1: Yes.
J = 1960
M = april
T = 1

Resolution 2: No.


?- zwillinge(_, _).

Resolution 1: Yes.

Resolution 2: No.


?- geschwister(gaby, X{0}).

Resolution 1: No.