A boy grinds a ledge on his skateboard.
A boy competes in a skateboard competition.
It is not necessary that he competes in a competition.
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 e1 s1 x1 x2.(in(e1,x2) & n_competition(x2) & a_skateboard(s1) & Theme(s1,x2) & Actor(e1,x1) & v_compete(e1) & n_boy(x1))