Definition smvalid_src (mu : SM_Injection) m1 :=
  forall b1, DOM mu b1 -> Memory.Mem.valid_block m1 b1.Definition smvalid_tgt (mu : SM_Injection) m2 :=
  forall b2, RNG mu b2 -> Memory.Mem.valid_block m2 b2.

Lemma extern_incr_refl: forall mu, extern_incr mu mu.