The boy is skateboarding on the bench by the fence.
The boy is skateboarding over the bench on his way to the park.
Someone skateboarding on a bench may not be skateboarding over the bench. A boy skateboarding on a bench may not be on his way to the park.
exists e1 x1 x2 x3.(n_fence(x3) & n_bench(x2) & n_boy(x1) & by(e1,x3) & on(e1,x2) & Actor(e1,x1) & v_skateboard(e1))
exists e1 x1 x2 x3 x4.(n_bench(x2) & n_park(x4) & n_way(x3) & of(x3,x2) & n_male(x2) & n_boy(x1) & over(e1,x2) & on(e1,x3) & to(x3,x4) & Actor(e1,x1) & v_skateboard(e1))