a skateboarder grinds the rail.
A skateboarder in action
When skateboarder grind th rail is in action performing tricks with the skateboard.
exists e1 x1 x2.(n_rail(x2) & Theme(e1,x2) & Actor(e1,x1) & v_grind(e1) & n_skateboarder(x1))
exists x1 x2.(a_topic(x1) & in(x1,x2) & n_action(x2) & n_skateboarder(x1))