A man cleaning the top of a roof.
A tree fell on the roof.
We don't know that a tree fell.
exists e1 x1 x2 x3 x4.(n_top(x3) & a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_clean(e1) & of(x3,x4) & n_roof(x4) & (x1 = x2) & n_man(x1))
exists e1 x1 x2.(n_roof(x2) & on(e1,x2) & Actor(e1,x1) & v_fall(e1) & n_tree(x1))