A boy on a skateboard grinding down a handrail.
The boy is on a bicycle.
skateboard is not a bicycle
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & on(x1,x2) & a_down(s1) & Manner(e1,s1) & Theme(e1,x4) & Actor(e1,x3) & v_grind(e1) & n_handrail(x4) & (x2 = x3) & n_skateboard(x2) & n_boy(x1))
exists p1 x1.(n_boy(x1) & exists x2.(on(x1,x2) & n_bicycle(x2)))