a woman sits on the rock.
A woman is riding her bicycle.
Rock and bicycle are different.
exists e1 x1 x2.(n_rock(x2) & on(e1,x2) & Actor(e1,x1) & v_sit(e1) & n_woman(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bicycle(x2) & of(x2,x1) & n_female(x1) & n_woman(x1))