a skateboarder grinds the rail.
A skateboarder tries a new trick.
Grinding the rail does not imply this is a new trick.
exists e1 x1 x2.(n_rail(x2) & Theme(e1,x2) & Actor(e1,x1) & v_grind(e1) & n_skateboarder(x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_try(e1) & n_trick(x2) & a_new(s1) & Theme(s1,x2) & n_skateboarder(x1))