A man is grinding his skateboard on a guard rail.
The man rides skateboards.
If he owns a skateboard and is grinding it, it is implied that he rides them.
exists e1 x1 x2 x3 x4.(Theme(e1,x2) & Actor(e1,x1) & v_grind(e1) & on(x2,x3) & n_rail(x3) & of(x3,x4) & n_guard(x4) & n_skateboard(x2) & of(x2,x1) & n_male(x1) & n_man(x1))
exists e1 x1 x2.(n_man(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_skateboard(x2))