A man sitting on top of an unfinished structure.
A man wearing a hard hat is sitting on an unfinished structure.
A man sitting on top of an unfinished structure doesn't have to be wearing a hard hat.
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x3) & of(x3,x4) & n_structure(x4) & a_unfinished(s1) & Theme(s1,x4) & n_top(x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_man(x1))
exists e1 e2 s1 s2 x1 x2 x3 x4.(on(e2,x4) & n_structure(x4) & a_unfinished(s2) & Theme(s2,x4) & Actor(e2,x1) & v_sit(e2) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_hat(x3) & a_hard(s1) & Theme(s1,x3) & (x1 = x2) & n_man(x1))