The boy does a skateboard trick.
A boy does a kickflip.
A boy doing a skateboard trick isn't necessarily a kickflip.
exists e1 x1 x2 x3.(n_boy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_trick(x2) & of(x2,x3) & n_skateboard(x3))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_kickflip(x2) & n_boy(x1))