A male is standing in front of a wall will graffiti on the wall.
the rocks were hard
the wall may not be made of rocks
exists e2 e1 x1 x2 x3 x4.(in(e1,x2) & of(x2,x3) & on(e2,x3) & n_wall(x3) & n_wall(x3) & Actor(e2,x4) & v_graffiti(e2) & (x3 = x4) & n_front(x2) & Actor(e1,x1) & v_stand(e1) & n_male(x1))
exists s1 x1.(n_rock(x1) & Theme(s1,x1) & a_hard(s1))