A young man wears a helmet and protective clothing as he races his dirt bike through a muddy track.
A dirt biker is competing in a race.
A dirt bike rider on a muddy track does not imply that it is a race.
(-x)
exists e1 x1 x2 x3.(in(e1,x3) & n_race(x3) & Actor(e1,x1) & v_compete(e1) & n_biker(x1) & of(x1,x2) & n_dirt(x2))