A person in a white helmet is standing next to a ladder.
A person is wearing a black helmet
A person wearing a white helmet cannot be wearing a black helmet at the same time
exists e1 s1 x1 x2 x3.(to(e1,x3) & n_ladder(x3) & r_next(e1) & Actor(e1,x1) & v_stand(e1) & in(x1,x2) & n_helmet(x2) & a_white(s1) & Theme(s1,x2) & n_person(x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_helmet(x2) & a_black(s1) & Theme(s1,x2) & n_person(x1))