A boy grinds a ledge on his skateboard.
Boy riding skateboard at park
Even if it is not a park the boy can ride skateboard.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_grind(e1) & on(x2,x3) & n_skateboard(x3) & of(x3,x1) & n_male(x1) & n_ledge(x2) & n_boy(x1))
exists x1 x2 x3 x4.(a_topic(x1) & at(x1,x4) & n_park(x4) & n_skateboard(x1) & of(x1,x3) & n_riding(x3) & (x1 = x2) & ne_nam_boy(x2))