People walk down steps.
People walk down steps to basement
Downward stairs don't always lead to a basement.
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_step(x2) & a_down(s1) & Theme(s1,x2) & n_people(x1))
exists e1 s1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & to(x2,x3) & n_basement(x3) & n_step(x2) & a_down(s1) & Theme(s1,x2) & n_people(x1))