diff --git a/theories/Core/Soundness/LogicalRelation.v b/theories/Core/Soundness/LogicalRelation.v
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+++ b/theories/Core/Soundness/LogicalRelation.v
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+From Coq Require Import Relation_Definitions RelationClasses.
+From Mcltt Require Import Base LibTactics.
+From Mcltt.Core Require Import System.Definitions Evaluation Readback PER.Definitions.
+From Mcltt Require Export Domain.
+
+Import Domain_Notations.
+Global Open Scope predicate_scope.
+
+Generalizable All Variables.
+
+Notation "'typ_pred'" := (predicate (Tcons typ Tnil)).
+Notation "'glu_pred'" := (predicate (Tcons exp (Tcons typ (Tcons domain Tnil)))).
+
+Definition univ_typ_pred Γ j i : typ_pred := fun T => {{ Γ ⊢ T ≈ Type@j :  Type@i }}.
+
+Section Gluing.
+  Variable
+    (i : nat)
+      (glu_univ_rec : forall {j}, j < i -> relation domain)
+      (glu_univ_typ_rec : forall {j}, j < i -> typ_pred).
+
+  Definition univ_glu_pred Γ {j} (lt_j_i : j < i) : glu_pred :=
+    fun m M A =>
+    {{ Γ ⊢ m : M }} /\ {{ Γ ⊢ M ≈ Type@j : Type@i }} /\
+      glu_univ_rec lt_j_i A A /\
+      glu_univ_typ_rec lt_j_i m.
+
+  Inductive glu_univ_elem_core : ctx -> relation domain -> typ_pred -> glu_pred -> domain -> domain -> Prop :=
+  | glu_univ_elem_core_univ :
+    `{ forall (elem_rel : relation domain)
+         typ_rel
+         el_rel
+         (lt_j_i : j < i),
+          j = j' ->
+          (elem_rel <~> glu_univ_rec lt_j_i) ->
+          typ_rel <∙> univ_typ_pred Γ j i ->
+          el_rel <∙> univ_glu_pred Γ lt_j_i ->
+          glu_univ_elem_core Γ elem_rel typ_rel el_rel d{{{ 𝕌@j }}} d{{{ 𝕌@j' }}} }.
+
+  (* | per_univ_elem_core_nat : *)
+  (*   forall (elem_rel : relation domain), *)
+  (*     (elem_rel <~> per_nat) -> *)
+  (*     {{ DF ℕ ≈ ℕ ∈ per_univ_elem_core ↘ elem_rel }} *)
+  (* | per_univ_elem_core_pi : *)
+  (*   `{ forall (in_rel : relation domain) *)
+  (*        (out_rel : forall {c c'} (equiv_c_c' : {{ Dom c ≈ c' ∈ in_rel }}), relation domain) *)
+  (*        (elem_rel : relation domain) *)
+  (*        (equiv_a_a' : {{ DF a ≈ a' ∈ per_univ_elem_core ↘ in_rel}}), *)
+  (*         PER in_rel -> *)
+  (*         (forall {c c'} (equiv_c_c' : {{ Dom c ≈ c' ∈ in_rel }}), *)
+  (*             rel_mod_eval per_univ_elem_core B d{{{ p ↦ c }}} B' d{{{ p' ↦ c' }}} (out_rel equiv_c_c')) -> *)
+  (*         (elem_rel <~> fun f f' => forall c c' (equiv_c_c' : {{ Dom c ≈ c' ∈ in_rel }}), rel_mod_app f c f' c' (out_rel equiv_c_c')) -> *)
+  (*         {{ DF Π a p B ≈ Π a' p' B' ∈ per_univ_elem_core ↘ elem_rel }} } *)
+  (* | per_univ_elem_core_neut : *)
+  (*   `{ forall (elem_rel : relation domain), *)
+  (*         {{ Dom b ≈ b' ∈ per_bot }} -> *)
+  (*         (elem_rel <~> per_ne) -> *)
+  (*         {{ DF ⇑ a b ≈ ⇑ a' b' ∈ per_univ_elem_core ↘ elem_rel }} } *)
+  (* . *)