A teenage boy grinds his skateboard over a red rail.
A young boy was doing tricks on his skateboard.
When someone grinds their skateboard over a rail, they are doing tricks.
exists e1 s1 x1 x2 x3 x4.(Theme(e1,x3) & Actor(e1,x1) & v_grind(e1) & over(x3,x4) & n_rail(x4) & a_red(s1) & Theme(s1,x4) & n_skateboard(x3) & of(x3,x1) & n_male(x1) & n_boy(x1) & of(x1,x2) & n_teenage(x2))
exists e1 s1 x1 x2 x3.(on(e1,x3) & n_skateboard(x3) & of(x3,x1) & n_male(x1) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_trick(x2) & n_boy(x1) & a_young(s1) & Theme(s1,x1))