A child jumps on a sand dune.
The child is at the beach.
The is nothing to indicate that the sand dune is at the beach rather than in a desert.
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 p1 x1 x2.(n_beach(x2) & n_child(x1) & at(x1,x2))