People walk down a wet sidewalk.
People are walking down a slippery sidewalk.
Are walking is rephrasing of walk down and wet sidewalk will be slippery sidewalk.
exists e1 s1 x1 x2.(down(e1,x2) & n_sidewalk(x2) & a_wet(s1) & Theme(s1,x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1))
exists e1 s1 x1 x2 x3.(a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_sidewalk(x2) & of(x2,x3) & n_slippery(x3) & n_people(x1))