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-rwxr-xr-xtheories/Relations/Newman.v123
-rwxr-xr-xtheories/Relations/Operators_Properties.v96
-rwxr-xr-xtheories/Relations/Relation_Definitions.v78
-rwxr-xr-xtheories/Relations/Relation_Operators.v167
-rwxr-xr-xtheories/Relations/Relations.v28
-rwxr-xr-xtheories/Relations/Rstar.v87
-rwxr-xr-xtheories/Relations/intro.tex23
7 files changed, 602 insertions, 0 deletions
diff --git a/theories/Relations/Newman.v b/theories/Relations/Newman.v
new file mode 100755
index 00000000..3cf604d8
--- /dev/null
+++ b/theories/Relations/Newman.v
@@ -0,0 +1,123 @@
+(************************************************************************)
+(* v * The Coq Proof Assistant / The Coq Development Team *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(* \VV/ **************************************************************)
+(* // * This file is distributed under the terms of the *)
+(* * GNU Lesser General Public License Version 2.1 *)
+(************************************************************************)
+
+(*i $Id: Newman.v,v 1.7.2.1 2004/07/16 19:31:16 herbelin Exp $ i*)
+
+Require Import Rstar.
+
+Section Newman.
+
+Variable A : Type.
+Variable R : A -> A -> Prop.
+
+Let Rstar := Rstar A R.
+Let Rstar_reflexive := Rstar_reflexive A R.
+Let Rstar_transitive := Rstar_transitive A R.
+Let Rstar_Rstar' := Rstar_Rstar' A R.
+
+Definition coherence (x y:A) := ex2 (Rstar x) (Rstar y).
+
+Theorem coherence_intro :
+ forall x y z:A, Rstar x z -> Rstar y z -> coherence x y.
+Proof
+ fun (x y z:A) (h1:Rstar x z) (h2:Rstar y z) =>
+ ex_intro2 (Rstar x) (Rstar y) z h1 h2.
+
+(** A very simple case of coherence : *)
+
+Lemma Rstar_coherence : forall x y:A, Rstar x y -> coherence x y.
+ Proof
+ fun (x y:A) (h:Rstar x y) => coherence_intro x y y h (Rstar_reflexive y).
+
+(** coherence is symmetric *)
+Lemma coherence_sym : forall x y:A, coherence x y -> coherence y x.
+ Proof
+ fun (x y:A) (h:coherence x y) =>
+ ex2_ind
+ (fun (w:A) (h1:Rstar x w) (h2:Rstar y w) =>
+ coherence_intro y x w h2 h1) h.
+
+Definition confluence (x:A) :=
+ forall y z:A, Rstar x y -> Rstar x z -> coherence y z.
+
+Definition local_confluence (x:A) :=
+ forall y z:A, R x y -> R x z -> coherence y z.
+
+Definition noetherian :=
+ forall (x:A) (P:A -> Prop),
+ (forall y:A, (forall z:A, R y z -> P z) -> P y) -> P x.
+
+Section Newman_section.
+
+(** The general hypotheses of the theorem *)
+
+Hypothesis Hyp1 : noetherian.
+Hypothesis Hyp2 : forall x:A, local_confluence x.
+
+(** The induction hypothesis *)
+
+Section Induct.
+ Variable x : A.
+ Hypothesis hyp_ind : forall u:A, R x u -> confluence u.
+
+(** Confluence in [x] *)
+
+ Variables y z : A.
+ Hypothesis h1 : Rstar x y.
+ Hypothesis h2 : Rstar x z.
+
+(** particular case [x->u] and [u->*y] *)
+Section Newman_.
+ Variable u : A.
+ Hypothesis t1 : R x u.
+ Hypothesis t2 : Rstar u y.
+
+(** In the usual diagram, we assume also [x->v] and [v->*z] *)
+
+Theorem Diagram : forall (v:A) (u1:R x v) (u2:Rstar v z), coherence y z.
+
+Proof
+ (* We draw the diagram ! *)
+ fun (v:A) (u1:R x v) (u2:Rstar v z) =>
+ ex2_ind
+ (* local confluence in x for u,v *)
+ (* gives w, u->*w and v->*w *)
+ (fun (w:A) (s1:Rstar u w) (s2:Rstar v w) =>
+ ex2_ind
+ (* confluence in u => coherence(y,w) *)
+ (* gives a, y->*a and z->*a *)
+ (fun (a:A) (v1:Rstar y a) (v2:Rstar w a) =>
+ ex2_ind
+ (* confluence in v => coherence(a,z) *)
+ (* gives b, a->*b and z->*b *)
+ (fun (b:A) (w1:Rstar a b) (w2:Rstar z b) =>
+ coherence_intro y z b (Rstar_transitive y a b v1 w1) w2)
+ (hyp_ind v u1 a z (Rstar_transitive v w a s2 v2) u2))
+ (hyp_ind u t1 y w t2 s1)) (Hyp2 x u v t1 u1).
+
+Theorem caseRxy : coherence y z.
+Proof
+ Rstar_Rstar' x z h2 (fun v w:A => coherence y w)
+ (coherence_sym x y (Rstar_coherence x y h1)) (*i case x=z i*)
+ Diagram. (*i case x->v->*z i*)
+End Newman_.
+
+Theorem Ind_proof : coherence y z.
+Proof
+ Rstar_Rstar' x y h1 (fun u v:A => coherence v z)
+ (Rstar_coherence x z h2) (*i case x=y i*)
+ caseRxy. (*i case x->u->*z i*)
+End Induct.
+
+Theorem Newman : forall x:A, confluence x.
+Proof fun x:A => Hyp1 x confluence Ind_proof.
+
+End Newman_section.
+
+
+End Newman.
diff --git a/theories/Relations/Operators_Properties.v b/theories/Relations/Operators_Properties.v
new file mode 100755
index 00000000..5e0e9ec8
--- /dev/null
+++ b/theories/Relations/Operators_Properties.v
@@ -0,0 +1,96 @@
+(************************************************************************)
+(* v * The Coq Proof Assistant / The Coq Development Team *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(* \VV/ **************************************************************)
+(* // * This file is distributed under the terms of the *)
+(* * GNU Lesser General Public License Version 2.1 *)
+(************************************************************************)
+
+(*i $Id: Operators_Properties.v,v 1.7.2.1 2004/07/16 19:31:16 herbelin Exp $ i*)
+
+(****************************************************************************)
+(* Bruno Barras *)
+(****************************************************************************)
+
+Require Import Relation_Definitions.
+Require Import Relation_Operators.
+
+
+Section Properties.
+
+ Variable A : Set.
+ Variable R : relation A.
+
+ Let incl (R1 R2:relation A) : Prop := forall x y:A, R1 x y -> R2 x y.
+
+Section Clos_Refl_Trans.
+
+ Lemma clos_rt_is_preorder : preorder A (clos_refl_trans A R).
+apply Build_preorder.
+exact (rt_refl A R).
+
+exact (rt_trans A R).
+Qed.
+
+
+
+Lemma clos_rt_idempotent :
+ incl (clos_refl_trans A (clos_refl_trans A R)) (clos_refl_trans A R).
+red in |- *.
+induction 1; auto with sets.
+intros.
+apply rt_trans with y; auto with sets.
+Qed.
+
+ Lemma clos_refl_trans_ind_left :
+ forall (A:Set) (R:A -> A -> Prop) (M:A) (P:A -> Prop),
+ P M ->
+ (forall P0 N:A, clos_refl_trans A R M P0 -> P P0 -> R P0 N -> P N) ->
+ forall a:A, clos_refl_trans A R M a -> P a.
+intros.
+generalize H H0.
+clear H H0.
+elim H1; intros; auto with sets.
+apply H2 with x; auto with sets.
+
+apply H3.
+apply H0; auto with sets.
+
+intros.
+apply H5 with P0; auto with sets.
+apply rt_trans with y; auto with sets.
+Qed.
+
+
+End Clos_Refl_Trans.
+
+
+Section Clos_Refl_Sym_Trans.
+
+ Lemma clos_rt_clos_rst :
+ inclusion A (clos_refl_trans A R) (clos_refl_sym_trans A R).
+red in |- *.
+induction 1; auto with sets.
+apply rst_trans with y; auto with sets.
+Qed.
+
+ Lemma clos_rst_is_equiv : equivalence A (clos_refl_sym_trans A R).
+apply Build_equivalence.
+exact (rst_refl A R).
+
+exact (rst_trans A R).
+
+exact (rst_sym A R).
+Qed.
+
+ Lemma clos_rst_idempotent :
+ incl (clos_refl_sym_trans A (clos_refl_sym_trans A R))
+ (clos_refl_sym_trans A R).
+red in |- *.
+induction 1; auto with sets.
+apply rst_trans with y; auto with sets.
+Qed.
+
+End Clos_Refl_Sym_Trans.
+
+End Properties. \ No newline at end of file
diff --git a/theories/Relations/Relation_Definitions.v b/theories/Relations/Relation_Definitions.v
new file mode 100755
index 00000000..e115b0b0
--- /dev/null
+++ b/theories/Relations/Relation_Definitions.v
@@ -0,0 +1,78 @@
+(************************************************************************)
+(* v * The Coq Proof Assistant / The Coq Development Team *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(* \VV/ **************************************************************)
+(* // * This file is distributed under the terms of the *)
+(* * GNU Lesser General Public License Version 2.1 *)
+(************************************************************************)
+
+(*i $Id: Relation_Definitions.v,v 1.6.2.1 2004/07/16 19:31:16 herbelin Exp $ i*)
+
+Section Relation_Definition.
+
+ Variable A : Type.
+
+ Definition relation := A -> A -> Prop.
+
+ Variable R : relation.
+
+
+Section General_Properties_of_Relations.
+
+ Definition reflexive : Prop := forall x:A, R x x.
+ Definition transitive : Prop := forall x y z:A, R x y -> R y z -> R x z.
+ Definition symmetric : Prop := forall x y:A, R x y -> R y x.
+ Definition antisymmetric : Prop := forall x y:A, R x y -> R y x -> x = y.
+
+ (* for compatibility with Equivalence in ../PROGRAMS/ALG/ *)
+ Definition equiv := reflexive /\ transitive /\ symmetric.
+
+End General_Properties_of_Relations.
+
+
+
+Section Sets_of_Relations.
+
+ Record preorder : Prop :=
+ {preord_refl : reflexive; preord_trans : transitive}.
+
+ Record order : Prop :=
+ {ord_refl : reflexive;
+ ord_trans : transitive;
+ ord_antisym : antisymmetric}.
+
+ Record equivalence : Prop :=
+ {equiv_refl : reflexive;
+ equiv_trans : transitive;
+ equiv_sym : symmetric}.
+
+ Record PER : Prop := {per_sym : symmetric; per_trans : transitive}.
+
+End Sets_of_Relations.
+
+
+
+Section Relations_of_Relations.
+
+ Definition inclusion (R1 R2:relation) : Prop :=
+ forall x y:A, R1 x y -> R2 x y.
+
+ Definition same_relation (R1 R2:relation) : Prop :=
+ inclusion R1 R2 /\ inclusion R2 R1.
+
+ Definition commut (R1 R2:relation) : Prop :=
+ forall x y:A,
+ R1 y x -> forall z:A, R2 z y -> exists2 y' : A, R2 y' x & R1 z y'.
+
+End Relations_of_Relations.
+
+
+End Relation_Definition.
+
+Hint Unfold reflexive transitive antisymmetric symmetric: sets v62.
+
+Hint Resolve Build_preorder Build_order Build_equivalence Build_PER
+ preord_refl preord_trans ord_refl ord_trans ord_antisym equiv_refl
+ equiv_trans equiv_sym per_sym per_trans: sets v62.
+
+Hint Unfold inclusion same_relation commut: sets v62. \ No newline at end of file
diff --git a/theories/Relations/Relation_Operators.v b/theories/Relations/Relation_Operators.v
new file mode 100755
index 00000000..b6359ada
--- /dev/null
+++ b/theories/Relations/Relation_Operators.v
@@ -0,0 +1,167 @@
+(************************************************************************)
+(* v * The Coq Proof Assistant / The Coq Development Team *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(* \VV/ **************************************************************)
+(* // * This file is distributed under the terms of the *)
+(* * GNU Lesser General Public License Version 2.1 *)
+(************************************************************************)
+
+(*i $Id: Relation_Operators.v,v 1.8.2.1 2004/07/16 19:31:16 herbelin Exp $ i*)
+
+(****************************************************************************)
+(* Bruno Barras, Cristina Cornes *)
+(* *)
+(* Some of these definitons were taken from : *)
+(* Constructing Recursion Operators in Type Theory *)
+(* L. Paulson JSC (1986) 2, 325-355 *)
+(****************************************************************************)
+
+Require Import Relation_Definitions.
+Require Import List.
+
+(** Some operators to build relations *)
+
+Section Transitive_Closure.
+ Variable A : Set.
+ Variable R : relation A.
+
+ Inductive clos_trans : A -> A -> Prop :=
+ | t_step : forall x y:A, R x y -> clos_trans x y
+ | t_trans :
+ forall x y z:A, clos_trans x y -> clos_trans y z -> clos_trans x z.
+End Transitive_Closure.
+
+
+Section Reflexive_Transitive_Closure.
+ Variable A : Set.
+ Variable R : relation A.
+
+ Inductive clos_refl_trans : relation A :=
+ | rt_step : forall x y:A, R x y -> clos_refl_trans x y
+ | rt_refl : forall x:A, clos_refl_trans x x
+ | rt_trans :
+ forall x y z:A,
+ clos_refl_trans x y -> clos_refl_trans y z -> clos_refl_trans x z.
+End Reflexive_Transitive_Closure.
+
+
+Section Reflexive_Symetric_Transitive_Closure.
+ Variable A : Set.
+ Variable R : relation A.
+
+ Inductive clos_refl_sym_trans : relation A :=
+ | rst_step : forall x y:A, R x y -> clos_refl_sym_trans x y
+ | rst_refl : forall x:A, clos_refl_sym_trans x x
+ | rst_sym :
+ forall x y:A, clos_refl_sym_trans x y -> clos_refl_sym_trans y x
+ | rst_trans :
+ forall x y z:A,
+ clos_refl_sym_trans x y ->
+ clos_refl_sym_trans y z -> clos_refl_sym_trans x z.
+End Reflexive_Symetric_Transitive_Closure.
+
+
+Section Transposee.
+ Variable A : Set.
+ Variable R : relation A.
+
+ Definition transp (x y:A) := R y x.
+End Transposee.
+
+
+Section Union.
+ Variable A : Set.
+ Variables R1 R2 : relation A.
+
+ Definition union (x y:A) := R1 x y \/ R2 x y.
+End Union.
+
+
+Section Disjoint_Union.
+Variables A B : Set.
+Variable leA : A -> A -> Prop.
+Variable leB : B -> B -> Prop.
+
+Inductive le_AsB : A + B -> A + B -> Prop :=
+ | le_aa : forall x y:A, leA x y -> le_AsB (inl B x) (inl B y)
+ | le_ab : forall (x:A) (y:B), le_AsB (inl B x) (inr A y)
+ | le_bb : forall x y:B, leB x y -> le_AsB (inr A x) (inr A y).
+
+End Disjoint_Union.
+
+
+
+Section Lexicographic_Product.
+(* Lexicographic order on dependent pairs *)
+
+Variable A : Set.
+Variable B : A -> Set.
+Variable leA : A -> A -> Prop.
+Variable leB : forall x:A, B x -> B x -> Prop.
+
+Inductive lexprod : sigS B -> sigS B -> Prop :=
+ | left_lex :
+ forall (x x':A) (y:B x) (y':B x'),
+ leA x x' -> lexprod (existS B x y) (existS B x' y')
+ | right_lex :
+ forall (x:A) (y y':B x),
+ leB x y y' -> lexprod (existS B x y) (existS B x y').
+End Lexicographic_Product.
+
+
+Section Symmetric_Product.
+ Variable A : Set.
+ Variable B : Set.
+ Variable leA : A -> A -> Prop.
+ Variable leB : B -> B -> Prop.
+
+ Inductive symprod : A * B -> A * B -> Prop :=
+ | left_sym :
+ forall x x':A, leA x x' -> forall y:B, symprod (x, y) (x', y)
+ | right_sym :
+ forall y y':B, leB y y' -> forall x:A, symprod (x, y) (x, y').
+
+End Symmetric_Product.
+
+
+Section Swap.
+ Variable A : Set.
+ Variable R : A -> A -> Prop.
+
+ Inductive swapprod : A * A -> A * A -> Prop :=
+ | sp_noswap : forall x x':A * A, symprod A A R R x x' -> swapprod x x'
+ | sp_swap :
+ forall (x y:A) (p:A * A),
+ symprod A A R R (x, y) p -> swapprod (y, x) p.
+End Swap.
+
+
+Section Lexicographic_Exponentiation.
+
+Variable A : Set.
+Variable leA : A -> A -> Prop.
+Let Nil := nil (A:=A).
+Let List := list A.
+
+Inductive Ltl : List -> List -> Prop :=
+ | Lt_nil : forall (a:A) (x:List), Ltl Nil (a :: x)
+ | Lt_hd : forall a b:A, leA a b -> forall x y:list A, Ltl (a :: x) (b :: y)
+ | Lt_tl : forall (a:A) (x y:List), Ltl x y -> Ltl (a :: x) (a :: y).
+
+
+Inductive Desc : List -> Prop :=
+ | d_nil : Desc Nil
+ | d_one : forall x:A, Desc (x :: Nil)
+ | d_conc :
+ forall (x y:A) (l:List),
+ leA x y -> Desc (l ++ y :: Nil) -> Desc ((l ++ y :: Nil) ++ x :: Nil).
+
+Definition Pow : Set := sig Desc.
+
+Definition lex_exp (a b:Pow) : Prop := Ltl (proj1_sig a) (proj1_sig b).
+
+End Lexicographic_Exponentiation.
+
+Hint Unfold transp union: sets v62.
+Hint Resolve t_step rt_step rt_refl rst_step rst_refl: sets v62.
+Hint Immediate rst_sym: sets v62. \ No newline at end of file
diff --git a/theories/Relations/Relations.v b/theories/Relations/Relations.v
new file mode 100755
index 00000000..6c96f14d
--- /dev/null
+++ b/theories/Relations/Relations.v
@@ -0,0 +1,28 @@
+(************************************************************************)
+(* v * The Coq Proof Assistant / The Coq Development Team *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(* \VV/ **************************************************************)
+(* // * This file is distributed under the terms of the *)
+(* * GNU Lesser General Public License Version 2.1 *)
+(************************************************************************)
+
+(*i $Id: Relations.v,v 1.6.2.1 2004/07/16 19:31:16 herbelin Exp $ i*)
+
+Require Export Relation_Definitions.
+Require Export Relation_Operators.
+Require Export Operators_Properties.
+
+Lemma inverse_image_of_equivalence :
+ forall (A B:Set) (f:A -> B) (r:relation B),
+ equivalence B r -> equivalence A (fun x y:A => r (f x) (f y)).
+intros; split; elim H; red in |- *; auto.
+intros _ equiv_trans _ x y z H0 H1; apply equiv_trans with (f y); assumption.
+Qed.
+
+Lemma inverse_image_of_eq :
+ forall (A B:Set) (f:A -> B), equivalence A (fun x y:A => f x = f y).
+split; red in |- *;
+ [ (* reflexivity *) reflexivity
+ | (* transitivity *) intros; transitivity (f y); assumption
+ | (* symmetry *) intros; symmetry in |- *; assumption ].
+Qed. \ No newline at end of file
diff --git a/theories/Relations/Rstar.v b/theories/Relations/Rstar.v
new file mode 100755
index 00000000..7bb3ee93
--- /dev/null
+++ b/theories/Relations/Rstar.v
@@ -0,0 +1,87 @@
+(************************************************************************)
+(* v * The Coq Proof Assistant / The Coq Development Team *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(* \VV/ **************************************************************)
+(* // * This file is distributed under the terms of the *)
+(* * GNU Lesser General Public License Version 2.1 *)
+(************************************************************************)
+
+(*i $Id: Rstar.v,v 1.8.2.1 2004/07/16 19:31:16 herbelin Exp $ i*)
+
+(** Properties of a binary relation [R] on type [A] *)
+
+Section Rstar.
+
+Variable A : Type.
+Variable R : A -> A -> Prop.
+
+(** Definition of the reflexive-transitive closure [R*] of [R] *)
+(** Smallest reflexive [P] containing [R o P] *)
+
+Definition Rstar (x y:A) :=
+ forall P:A -> A -> Prop,
+ (forall u:A, P u u) -> (forall u v w:A, R u v -> P v w -> P u w) -> P x y.
+
+Theorem Rstar_reflexive : forall x:A, Rstar x x.
+ Proof
+ fun (x:A) (P:A -> A -> Prop) (h1:forall u:A, P u u)
+ (h2:forall u v w:A, R u v -> P v w -> P u w) =>
+ h1 x.
+
+Theorem Rstar_R : forall x y z:A, R x y -> Rstar y z -> Rstar x z.
+ Proof
+ fun (x y z:A) (t1:R x y) (t2:Rstar y z) (P:A -> A -> Prop)
+ (h1:forall u:A, P u u) (h2:forall u v w:A, R u v -> P v w -> P u w) =>
+ h2 x y z t1 (t2 P h1 h2).
+
+(** We conclude with transitivity of [Rstar] : *)
+
+Theorem Rstar_transitive :
+ forall x y z:A, Rstar x y -> Rstar y z -> Rstar x z.
+ Proof
+ fun (x y z:A) (h:Rstar x y) =>
+ h (fun u v:A => Rstar v z -> Rstar u z) (fun (u:A) (t:Rstar u z) => t)
+ (fun (u v w:A) (t1:R u v) (t2:Rstar w z -> Rstar v z)
+ (t3:Rstar w z) => Rstar_R u v z t1 (t2 t3)).
+
+(** Another characterization of [R*] *)
+(** Smallest reflexive [P] containing [R o R*] *)
+
+Definition Rstar' (x y:A) :=
+ forall P:A -> A -> Prop,
+ P x x -> (forall u:A, R x u -> Rstar u y -> P x y) -> P x y.
+
+Theorem Rstar'_reflexive : forall x:A, Rstar' x x.
+ Proof
+ fun (x:A) (P:A -> A -> Prop) (h:P x x)
+ (h':forall u:A, R x u -> Rstar u x -> P x x) => h.
+
+Theorem Rstar'_R : forall x y z:A, R x z -> Rstar z y -> Rstar' x y.
+ Proof
+ fun (x y z:A) (t1:R x z) (t2:Rstar z y) (P:A -> A -> Prop)
+ (h1:P x x) (h2:forall u:A, R x u -> Rstar u y -> P x y) =>
+ h2 z t1 t2.
+
+(** Equivalence of the two definitions: *)
+
+Theorem Rstar'_Rstar : forall x y:A, Rstar' x y -> Rstar x y.
+ Proof
+ fun (x y:A) (h:Rstar' x y) =>
+ h Rstar (Rstar_reflexive x) (fun u:A => Rstar_R x u y).
+
+Theorem Rstar_Rstar' : forall x y:A, Rstar x y -> Rstar' x y.
+ Proof
+ fun (x y:A) (h:Rstar x y) =>
+ h Rstar' (fun u:A => Rstar'_reflexive u)
+ (fun (u v w:A) (h1:R u v) (h2:Rstar' v w) =>
+ Rstar'_R u w v h1 (Rstar'_Rstar v w h2)).
+
+
+(** Property of Commutativity of two relations *)
+
+Definition commut (A:Set) (R1 R2:A -> A -> Prop) :=
+ forall x y:A,
+ R1 y x -> forall z:A, R2 z y -> exists2 y' : A, R2 y' x & R1 z y'.
+
+
+End Rstar.
diff --git a/theories/Relations/intro.tex b/theories/Relations/intro.tex
new file mode 100755
index 00000000..5056f36f
--- /dev/null
+++ b/theories/Relations/intro.tex
@@ -0,0 +1,23 @@
+\section{Relations}\label{Relations}
+
+This library develops closure properties of relations.
+
+\begin{itemize}
+\item {\tt Relation\_Definitions.v} deals with the general notions
+ about binary relations (orders, equivalences, ...)
+
+\item {\tt Relation\_Operators.v} and {\tt Rstar.v} define various
+ closures of relations (by symmetry, by transitivity, ...) and
+ lexicographic orderings.
+
+\item {\tt Operators\_Properties.v} states and proves facts on the
+ various closures of a relation.
+
+\item {\tt Relations.v} puts {\tt Relation\_Definitions.v}, {\tt
+ Relation\_Operators.v} and \\
+ {\tt Operators\_Properties.v} together.
+
+\item {\tt Newman.v} proves Newman's lemma on noetherian and locally
+ confluent relations.
+
+\end{itemize}