A man is standing behind a giant green machine.
A man is standing next to a giant green machine, waiting for his picture to be taken.
A man standing behind a machine is not necessarily waiting for his picture to be taken.
exists e1 s1 s2 x1 x2.(behind(e1,x2) & n_machine(x2) & a_green(s2) & Theme(s2,x2) & a_giant(s1) & Theme(s1,x2) & Actor(e1,x1) & v_stand(e1) & n_man(x1))
exists e1 e2 p1 s1 s2 x1 x2 x3.(for(e1,e2) & for(e2,x3) & Topic(x3,p1) & exists e3.(Theme(e3,x3) & v_take(e3)) & n_picture(x3) & of(x3,x1) & n_male(x1) & Actor(e2,x1) & v_wait(e2) & to(e1,x2) & n_machine(x2) & a_green(s2) & Theme(s2,x2) & a_giant(s1) & Theme(s1,x2) & r_next(e1) & Actor(e1,x1) & v_stand(e1) & n_man(x1))