Three children playing on a swing set.
Three sisters are swinging on swings.
Children can play on a swing set without swinging on the swings, and three children doesn't necessary imply that they are all three sisters.
exists e1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x3) & n_set(x3) & of(x3,x4) & n_swing(x4) & Actor(e1,x2) & v_play(e1) & (x1 = x2) & n_child(x1) & card_eq_3(x1))
exists e1 x1 x2.(on(e1,x2) & n_swing(x2) & Actor(e1,x1) & v_swing(e1) & n_sister(x1) & card_eq_3(x1))