A snowboarder is flying in the air attempting to land on a snow mound.
A skateboarder grinding on a rail.
First they were a snowboarder, then a skateboarder. you cannot be grinding and flying.
exists e1 e2 p1 x1 x2 x3.(n_air(x2) & in(e1,x2) & Topic(e2,p1) & Actor(e2,x3) & v_attempt(e2) & exists e3 x4 x5.(on(e3,x4) & n_mound(x4) & of(x4,x5) & n_snow(x5) & Actor(e3,x3) & v_land(e3)) & (x2 = x3) & Actor(e1,x1) & v_fly(e1) & n_snowboarder(x1))
exists e1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_rail(x3) & Actor(e1,x2) & v_grind(e1) & (x1 = x2) & n_skateboarder(x1))