A baby is playing in a walker.
A child inside smiling.
A baby in a walker would not necessarily be smiling.
exists e1 x1 x2.(in(e1,x2) & n_walker(x2) & Actor(e1,x1) & v_play(e1) & n_baby(x1))
exists x1 x2.(a_topic(x1) & inside(x1,x2) & n_smile(x2) & n_child(x1))