People on a subway.
People sit on the subway.
Being on the subway does not imply to sit.
exists x1 x2.(a_topic(x1) & on(x1,x2) & n_subway(x2) & n_people(x1))
exists e1 x1 x2.(n_subway(x2) & on(e1,x2) & Actor(e1,x1) & v_sit(e1) & n_people(x1))