A woman and boy sit on a police motorcycle.
A woman is riding a motorcycle while her son is holding onto her.
Someone sitting on a motorcycle might not be riding on it
exists e1 x1 x2 x3 x4 x5.(on(e1,x4) & n_motorcycle(x4) & of(x4,x5) & n_police(x5) & Actor(e1,x1) & v_sit(e1) & n_boy(x3) & n_woman(x2) & subset_of(x3,x1) & subset_of(x2,x1))
exists e1 p1 x1 x2 x3.(exists e2 x1.(onto(e2,x1) & n_female(x1) & Actor(e2,x3) & v_hold(e2)) & n_son(x3) & of(x3,x1) & n_female(x1) & while(e1,p1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_motorcycle(x2) & n_woman(x1))