A guy with boots is on a ladder.
A guy is working on the roof.
You can not infer he is on the roof.
exists p1 x1 x2.(exists x3.(on(x1,x3) & n_ladder(x3)) & with(x1,x2) & n_boot(x2) & n_guy(x1))
exists e1 x1 x2.(n_roof(x2) & on(e1,x2) & Actor(e1,x1) & v_work(e1) & n_guy(x1))