Man working on a straw roof
Man working hard on a roof
A roof does not have to be straw.  A man does not have to be hard to be working on a roof.
exists e1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x3) & n_roof(x3) & of(x3,x4) & n_straw(x4) & Actor(e1,x2) & v_work(e1) & (x1 = x2) & n_man(x1))
exists e1 s1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_roof(x3) & a_hard(s1) & Manner(e1,s1) & Actor(e1,x2) & v_work(e1) & (x1 = x2) & n_man(x1))