A skateboarder doing maneuvers.
Someone is riding a skateboard.
Someone is riding a skateboard is another way to say skateboarder
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_do(e1) & n_maneuver(x3) & (x1 = x2) & n_skateboarder(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_skateboard(x2) & n_person(x1))