The man washes down the walkway.
A man washes the sidewalk in front of his store.
A walkway might be something other than a sidewalk. "In front of his store" assumes the location of the walkway which is not given.
exists e1 s1 x1 x2.(n_walkway(x2) & n_man(x1) & a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_wash(e1))
exists e1 x1 x2 x3 x4.(n_store(x4) & of(x4,x2) & n_male(x2) & n_sidewalk(x2) & Theme(e1,x2) & Actor(e1,x1) & v_wash(e1) & in(x2,x3) & of(x3,x4) & n_front(x3) & n_man(x1))