Rollerblades sliding on a railing.
black rollerblades
Not all rollerblades are black.
exists e1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_railing(x3) & Actor(e1,x2) & v_slide(e1) & (x1 = x2) & n_rollerblade(x1))
exists s1 x1.(n_rollerblade(x1) & a_black(s1) & Theme(s1,x1) & a_topic(x1))