The snowboarder is grinding on a silver rail in the nighttime snow.
The snowboarder is competing in a contest grinding on a silver rail.
Grinding on a rail does not imply competing.
exists e1 s1 x1 x2 x3 x4.(n_snow(x4) & a_nighttime(s1) & Theme(s1,x4) & n_snowboarder(x1) & on(e1,x2) & in(x2,x4) & n_rail(x2) & of(x2,x3) & n_silver(x3) & Actor(e1,x1) & v_grind(e1))
exists e2 e1 x1 x2 x3 x4 x5.(n_snowboarder(x1) & in(e1,x2) & on(e2,x4) & n_rail(x4) & of(x4,x5) & n_silver(x5) & Actor(e2,x3) & v_grind(e2) & (x2 = x3) & n_contest(x2) & Actor(e1,x1) & v_compete(e1))