A young man goes air-born while his skateboard spins underneath him.
The man is not wearing a helmet.
Not wearing a helmet is not implied by a man skateboarding.
exists e1 p1 p2 s1 x1 x2.(exists e2 s3 x1.(for(e2,s3) & Theme(s3,x2) & a_underneath(s3) & Theme(e2,x1) & Actor(e2,x2) & v_spin(e2) & n_male(x1)) & n_skateboard(x2) & of(x2,x1) & n_male(x1) & while(e1,p2) & exists s2.(Theme(s2,x1) & a_air-born(s2)) & Topic(e1,p1) & Actor(e1,x1) & v_go(e1) & n_man(x1) & a_young(s1) & Theme(s1,x1))
exists x1.(n_man(x1) & -exists e1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_helmet(x2)))