diff --git a/core/src/main/java/com/jdbernard/wdiwtlt/db/models/Model.java b/core/src/main/java/com/jdbernard/wdiwtlt/db/models/Model.java
index 018f4ae..f8b873a 100644
--- a/core/src/main/java/com/jdbernard/wdiwtlt/db/models/Model.java
+++ b/core/src/main/java/com/jdbernard/wdiwtlt/db/models/Model.java
@@ -3,13 +3,21 @@ package com.jdbernard.wdiwtlt.db.models;
 import javax.persistence.Entity;
 
 @Entity
-public class Model {
+public class Model implements Comparable<Model> {
     public Integer id;
 
     public boolean equals(Object thatObj) {
         if (thatObj == null) return false;
-        if (!(thatObj instanceof Model)) return false;
+        if (this.getClass() != thatObj.getClass()) return false;
 
         Model that = (Model) thatObj;
-        return this.id == that.id; }
+        return this.id.equals(that.id); }
+
+    public int compareTo(Model that) {
+        if (this.id == null) return -1;
+        if (this.getClass() != that.getClass()) {
+            return this.getClass().getSimpleName().compareTo(
+                that.getClass().getSimpleName()); }
+
+        return this.id.compareTo(that.id); }
 }