A man in a helmet is riding a bike.
A man is wearing a helmet and riding his bicycle.
The man with a helmet is riding his bike so it can be presumed he is wearing the helmet.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_ride(e1) & n_bike(x3) & in(x1,x2) & n_helmet(x2) & n_man(x1))
exists e1 e2 x1 x2 x3 x4.(Theme(e2,x4) & Actor(e2,x3) & v_ride(e2) & n_bicycle(x4) & of(x4,x1) & n_male(x1) & n_man(x3) & Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_helmet(x2) & n_man(x1))