A person on a bmx bike.
Someone riding a bicycle outside.
Being on a bike does not imply riding it outside.
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & n_bike(x2) & of(x2,x3) & n_bmx(x3) & n_person(x1))
exists e1 x1 x2 x3 x4.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_outside(x3) & of(x3,x4) & n_bicycle(x4) & (x1 = x2) & n_person(x1))