A man on rollerblades is doing a trick.
The man is doing tricks on a sidewalk
One can do rollerblading tricks in a number of places, not just on a sidewalk.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_do(e1) & n_trick(x3) & on(x1,x2) & n_rollerblade(x2) & n_man(x1))
exists e1 x1 x2 x3.(n_man(x1) & on(e1,x3) & n_sidewalk(x3) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_trick(x2))