A person in a green shirt skateboards.
A boy in a green shirt does a skateboard trick
A person on a skateboard is not always a boy.  A person riding a skateboard does not always do a trick.
exists s1 x1 x2 x3.(a_topic(x1) & in(x1,x2) & n_skateboard(x2) & of(x2,x3) & n_shirt(x3) & a_green(s1) & Theme(s1,x2) & n_person(x1))
exists e1 s1 x1 x2 x3 x4.(Theme(e1,x3) & Actor(e1,x1) & v_do(e1) & n_trick(x3) & of(x3,x4) & n_skateboard(x4) & in(x1,x2) & n_shirt(x2) & a_green(s1) & Theme(s1,x2) & n_boy(x1))