A halway has a sign that says "PORT DU CASQUE OBLIGATOIRE" and some graffiti.
The hallway is spotless.
If there is some graffiti, the hallway is not spotless.
exists e1 e2 x1 x2 x3 x4 x5 x6 x7 x8 x9.(ne_nam_obligatoire(x5) & (x5 = x8) & ne_nam_casque(x8) & (x5 = x7) & ne_nam_du(x7) & (x5 = x6) & ne_nam_port(x6) & Theme(e2,x2) & Actor(e2,x1) & v_have(e2) & Theme(e1,x4) & Actor(e1,x3) & v_say(e1) & subset_of(x9,x4) & n_graffitus(x9) & subset_of(x5,x4) & (x2 = x3) & n_sign(x2) & n_halway(x1))
exists s1 x1.(n_hallway(x1) & Theme(s1,x1) & a_spotless(s1))