Some people are walking down the sidewalk in a city.
A group of people are on a sidewalk.
The second sentence simplifies the first sentence regarding people on a sidewalk.
exists e1 x1 x2 x3.(n_sidewalk(x2) & down(e1,x2) & in(x2,x3) & n_city(x3) & Actor(e1,x1) & v_walk(e1) & n_people(x1))
exists p1 x1 x2.(exists x3.(on(x1,x3) & n_sidewalk(x3)) & of(x1,x2) & n_people(x2) & n_group(x1))