people on a miniature train.
People on a boat.
a train and a boat are not the same.
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & n_train(x2) & of(x2,x3) & n_miniature(x3) & n_people(x1))
exists x1 x2.(a_topic(x1) & on(x1,x2) & n_boat(x2) & n_people(x1))