People walk down a crowded street.
The people are marching in a parade
People walking down a crowded street are not necessary part any marching or a parade.
exists e1 s1 x1 x2.(down(e1,x2) & n_street(x2) & a_crowded(s1) & Theme(s1,x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1))
exists e1 x1 x2.(n_people(x1) & in(e1,x2) & n_parade(x2) & Actor(e1,x1) & v_march(e1))