Workers are cleaning railroad tracks.
Workers are taking a break.
Workers cannot be cleaning and taking a break at the same time.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_clean(e1) & n_track(x2) & of(x2,x3) & n_railroad(x3) & n_worker(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_take(e1) & n_break(x2) & n_worker(x1))