People walking across a crosswalk.
People are walking on the sidewalk
A crosswalk can be connected to a sidewalk and if there are people walking on the sidewalk there might also be people walking across a crosswalk.
exists e1 x1 x2 x3.(a_topic(x1) & across(e1,x3) & n_crosswalk(x3) & Actor(e1,x2) & v_walk(e1) & (x1 = x2) & n_people(x1))
exists e1 x1 x2.(n_sidewalk(x2) & on(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1))