A crossing guard wearing a hat.
The person is not wearing any clothing.
A hat is a piece of clothing so the person cannot be wearing a hat and not wearing any clothing at the same time.
exists e1 e2 x1 x2 x3.(a_topic(x1) & Theme(e2,x3) & Actor(e2,x2) & v_wear(e2) & n_hat(x3) & (x1 = x2) & n_guard(x1) & Actor(e1,x1) & v_cross(e1))
exists x1.(n_person(x1) & -all x2.(n_clothing(x2) -> exists e1.(Theme(e1,x2) & Actor(e1,x1) & v_wear(e1))))