A child jumps on a sand dune.
A boy plays in the sand.
The child is not necessarily a boy
exists e1 x1 x2 x3.(on(e1,x2) & n_dune(x2) & of(x2,x3) & n_sand(x3) & Actor(e1,x1) & v_jump(e1) & n_child(x1))
exists e1 x1 x2.(n_sand(x2) & in(e1,x2) & Actor(e1,x1) & v_play(e1) & n_boy(x1))