A restaurant worker is cleaning a seat.
A restaurant worker is eating off of a dirty seat.
cleaning a seat happens, eating off a  dirty one does not.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_clean(e1) & n_seat(x3) & n_worker(x1) & of(x1,x2) & n_restaurant(x2))
exists e1 s1 x1 x2 x3.(of(e1,x3) & n_seat(x3) & a_dirty(s1) & Theme(s1,x3) & r_off(e1) & Actor(e1,x1) & v_eat(e1) & n_worker(x1) & of(x1,x2) & n_restaurant(x2))