A couple walks down the sidewalk.
A man and woman are walking down the sidewalk.
Just because a couple walks down the sidewalk does not imply that a man and woman are walking down the sidewalk.
exists e1 s1 x1 x2.(n_sidewalk(x2) & a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_couple(x1))
exists e1 x1 x2 x3 x4.(n_sidewalk(x4) & down(e1,x4) & Actor(e1,x1) & v_walk(e1) & n_woman(x3) & n_man(x2) & subset_of(x3,x1) & subset_of(x2,x1))