Rollerblades sliding on a railing.
A person is rollerblading down a railing.
Not all rollerblades have a person.
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 e1 s1 x1 x2.(a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_rollerblade(e1) & n_railing(x2) & n_person(x1))