Definition gname := own.gname.Instance Inhabitant_preds : Inhabitant preds := NoneP.Program Instance exclusive_PCM A : Ghost := { valid a := True;
  Join_G := Join_lower (Join_discrete A) }.Definition excl {A} g a := own(RA := exclusive_PCM A) g (Some a) NoneP.Program Instance prod_PCM (GA GB: Ghost): Ghost := { G := @G GA * @G GB;
  valid a := valid (fst a) /\ valid (snd a); Join_G := Join_prod _ _ _ _ }.(* Can we use Santiago and Qinxiang's paper to simplify this? *)
Class PCM_order `{P : Ghost} (ord : G -> G -> Prop) := { ord_refl :> RelationClasses.Reflexive ord;
  ord_trans :> RelationClasses.Transitive ord;
  ord_lub : forall a b c, ord a c -> ord b c -> {c' | join a b c' /\ ord c' c};
  join_ord : forall a b c, join a b c -> ord a c /\ ord b c; ord_join : forall a b, ord b a -> join a b a }.(* Can we use Santiago and Qinxiang's paper to simplify this? *)
Class PCM_order `{P : Ghost} (ord : G -> G -> Prop) := { ord_refl :> RelationClasses.Reflexive ord;
  ord_trans :> RelationClasses.Transitive ord;
  ord_lub : forall a b c, ord a c -> ord b c -> {c' | join a b c' /\ ord c' c};
  join_ord : forall a b c, join a b c -> ord a c /\ ord b c; ord_join : forall a b, ord b a -> join a b a }.(* Can we use Santiago and Qinxiang's paper to simplify this? *)
Class PCM_order `{P : Ghost} (ord : G -> G -> Prop) := { ord_refl :> RelationClasses.Reflexive ord;
  ord_trans :> RelationClasses.Transitive ord;
  ord_lub : forall a b c, ord a c -> ord b c -> {c' | join a b c' /\ ord c' c};
  join_ord : forall a b c, join a b c -> ord a c /\ ord b c; ord_join : forall a b, ord b a -> join a b a }.(* Can we use Santiago and Qinxiang's paper to simplify this? *)
Class PCM_order `{P : Ghost} (ord : G -> G -> Prop) := { ord_refl :> RelationClasses.Reflexive ord;
  ord_trans :> RelationClasses.Transitive ord;
  ord_lub : forall a b c, ord a c -> ord b c -> {c' | join a b c' /\ ord c' c};
  join_ord : forall a b c, join a b c -> ord a c /\ ord b c; ord_join : forall a b, ord b a -> join a b a }.(* Can we use Santiago and Qinxiang's paper to simplify this? *)
Class PCM_order `{P : Ghost} (ord : G -> G -> Prop) := { ord_refl :> RelationClasses.Reflexive ord;
  ord_trans :> RelationClasses.Transitive ord;
  ord_lub : forall a b c, ord a c -> ord b c -> {c' | join a b c' /\ ord c' c};
  join_ord : forall a b c, join a b c -> ord a c /\ ord b c; ord_join : forall a b, ord b a -> join a b a }.(* Can we use Santiago and Qinxiang's paper to simplify this? *)
Class PCM_order `{P : Ghost} (ord : G -> G -> Prop) := { ord_refl :> RelationClasses.Reflexive ord;
  ord_trans :> RelationClasses.Transitive ord;
  ord_lub : forall a b c, ord a c -> ord b c -> {c' | join a b c' /\ ord c' c};
  join_ord : forall a b c, join a b c -> ord a c /\ ord b c; ord_join : forall a b, ord b a -> join a b a }.

Lemma join_ord_eq : forall a b, ord a b <-> exists c, join a c b.