A young girl on her bike in her underwear
A young girl is riding her bike.
It can be assumed that if the girl is on her bike, she is riding it, because that is the action done on a bike.
exists s1 x1 x2 x3.(a_topic(x1) & on(x1,x2) & in(x2,x3) & n_underwear(x3) & of(x3,x1) & n_female(x1) & n_female(x1) & n_bike(x2) & of(x2,x1) & n_girl(x1) & a_young(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2) & of(x2,x1) & n_female(x1) & n_girl(x1) & a_young(s1) & Theme(s1,x1))