A group of people on a walkway.
The people are sleeping.
One cannot be sleeping and on a walkway simultaneously.
exists x1 x2 x3.(a_topic(x1) & of(x1,x2) & on(x2,x3) & n_walkway(x3) & n_people(x2) & n_group(x1))
exists e1 x1.(n_people(x1) & Actor(e1,x1) & v_sleep(e1))