Children playing on the beach.
There are children at the beach.
Children in both.
exists e1 x1 x2 x3.(n_beach(x3) & a_topic(x1) & on(e1,x3) & Actor(e1,x2) & v_play(e1) & (x1 = x2) & n_child(x1))
exists p1 x1 x3.(n_beach(x3) & exists x2.((x1 = x2) & at(x2,x3) & n_child(x2)))