Students walking down the road.
Students run on a track.
Students can't run and be walking.
exists e1 x1 x2 x3.(n_road(x3) & a_topic(x1) & down(e1,x3) & Actor(e1,x2) & v_walk(e1) & (x1 = x2) & n_student(x1))
exists e1 x1 x2.(on(e1,x2) & n_track(x2) & Actor(e1,x1) & v_run(e1) & n_student(x1))