--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| A.Asperti, C.Sacerdoti Coen, *)
+(* ||A|| E.Tassi, S.Zacchiroli *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU Lesser General Public License Version 2.1 *)
+(* *)
+(**************************************************************************)
+
+set "baseuri" "cic:/matita/higher_order_defs/relations/".
+
+include "logic/connectives.ma".
+
+definition reflexive: \forall A:Type.\forall R:A \to A \to Prop.Prop
+\def
+\lambda A.\lambda R.\forall x:A.R x x.
+
+definition symmetric: \forall A:Type.\forall R:A \to A \to Prop.Prop
+\def
+\lambda A.\lambda R.\forall x,y:A.R x y \to R y x.
+
+definition transitive: \forall A:Type.\forall R:A \to A \to Prop.Prop
+\def
+\lambda A.\lambda R.\forall x,y,z:A.R x y \to R y z \to R x z.
+