Instance star_equiv_subrelation : subrelation star equiv.
Instance stepplus_equiv_subrelation : subrelation stepplus equiv.
Instance evaluatesin_equiv_subrelation n : subrelation (evaluatesin n) equiv.

(* Specifications: *)
Lemma stepplus_star_stepplus s s' t : s ≻^+ s' -> s' ≻* t ->  s ≻^+ t.
Lemma I_neq_Omega : ~ I ≡ Omega.