The boy has his mouth open
The boy is grinning.
Either the boy is grinning or has his mouth open, not both.
exists e1 x1 x2 x3.(n_open(x2) & of(x2,x3) & n_mouth(x3) & of(x2,x1) & n_male(x1) & n_boy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_have(e1))
exists e1 x1.(n_boy(x1) & Actor(e1,x1) & v_grin(e1))