The boy is performing a trick on a red rail with a skateboard.
The boy is riding a skateboard
If one is performing a trick on a skateboard, one is commonly riding said skateboard.
exists e1 s1 x1 x2 x3 x4.(n_boy(x1) & on(e1,x3) & with(x3,x4) & n_skateboard(x4) & n_rail(x3) & a_red(s1) & Theme(s1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_trick(x2))
exists e1 x1 x2.(n_boy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_skateboard(x2))