A man Rollerblades in a park.
The man is on a bike.
park and bike are different things
exists e1 x1 x2.(in(e1,x2) & n_park(x2) & Actor(e1,x1) & v_rollerblade(e1) & n_man(x1))
exists p1 x1.(n_man(x1) & exists x2.(on(x1,x2) & n_bike(x2)))