A boy grinds a ledge on his skateboard.
Boy riding skateboard
boy on his skateboard means boy riding 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.(n_skateboard(x1) & of(x1,x3) & n_riding(x3) & (x1 = x2) & ne_nam_boy(x2) & a_topic(x1))