Definition all_assertions_computable  :=
  forall (Espec: OracleKind) psi tx vx (Q: assert), 
     exists k,  assert_safe Espec psi tx vx k = Q.

Lemma assert_safe_last: forall {Espec: OracleKind} ge ve te st rho w, (forall w', age w w' -> assert_safe Espec ge ve te st rho w) -> assert_safe Espec ge ve te st rho w.