A man sitting on an empty train
A man is on a bus
A man can not be sitting on a empty train and a bus at the same time.
exists e1 s1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_train(x3) & a_empty(s1) & Theme(s1,x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_man(x1))
exists p1 x1.(exists x2.(on(x1,x2) & n_bus(x2)) & n_man(x1))