People in the city.
People in a city park
Not all people in the city are in the park.
exists x1 x2.(n_city(x2) & a_topic(x1) & in(x1,x2) & n_people(x1))
exists x1 x2 x3.(a_topic(x1) & in(x1,x2) & n_park(x2) & of(x2,x3) & n_city(x3) & n_people(x1))