One boy is pushing another boy on a swing.
Nobody is near the swing.
There is either a boy or nobody.
exists e1 x1 x2 x3.(on(e1,x3) & n_swing(x3) & Theme(e1,x2) & Actor(e1,x1) & v_push(e1) & n_boy(x2) & -(x2 = x1) & n_boy(x1) & n_boy(x1) & card_eq_1(x1))
exists x2.(n_swing(x2) & -exists p1 x1.(near(x1,x2) & n_person(x1)))