A child playing with a sword at the bottom of the stairs.
A kid using a sword near the stairs.
A child is a kid.  Playing with a sword is a way of using it.  To be at the bottom of the stairs indicates that one is near them.
exists x1 x2 x3 x4 x5.(n_stair(x5) & n_bottom(x4) & a_topic(x1) & at(x1,x4) & of(x4,x5) & with(x1,x3) & n_sword(x3) & n_playing(x1) & of(x1,x2) & n_child(x2))
exists e1 x1 x2 x3 x4.(n_stair(x4) & a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_use(e1) & near(x3,x4) & n_sword(x3) & (x1 = x2) & n_kid(x1))