A man in a helmet is riding a bike.
The man in a helmet is riding a sports bike.
A man doesn't have to ride a sports bike, it could be any kind of bike.
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 x1 x2 x3 x4.(n_man(x1) & Theme(e1,x3) & Actor(e1,x1) & v_ride(e1) & n_bike(x3) & of(x3,x4) & n_sport(x4) & in(x1,x2) & n_helmet(x2))