People walk along a sidewalk in a city.
people walk on the sidewalk
on and along are the same thing.
exists e1 x1 x2 x3.(along(e1,x2) & in(x2,x3) & n_city(x3) & n_sidewalk(x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1))
exists e1 x1 x2.(n_sidewalk(x2) & on(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1))