A snowboarder glides through the air.
A snowboarder is going downhill.
Gliding through the air doesn't  necessarily mean that someone is going downhill.
exists e1 x1 x2.(n_air(x2) & through(e1,x2) & Actor(e1,x1) & v_glide(e1) & n_snowboarder(x1))
exists e1 s1 x1.(a_downhill(s1) & Manner(e1,s1) & Actor(e1,x1) & v_go(e1) & n_snowboarder(x1))