made the classes serializable

diff --git a/mavibot/src/main/java/org/apache/directory/mavibot/btree/RevisionName.java b/mavibot/src/main/java/org/apache/directory/mavibot/btree/RevisionName.java
index ae7a24f..1483168 100644
--- a/mavibot/src/main/java/org/apache/directory/mavibot/btree/RevisionName.java
+++ b/mavibot/src/main/java/org/apache/directory/mavibot/btree/RevisionName.java
@@ -31,6 +31,14 @@
 /* no qualifier*/class RevisionName extends Tuple<Long, String> implements Serializable
 {
     /**
+     * for serialization purpose
+     */
+    protected RevisionName()
+    {
+    }
+    
+    
+    /**
      * A constructor for the RevisionName class
      * @param revision The revision
      * @param name The BTree name
diff --git a/mavibot/src/main/java/org/apache/directory/mavibot/btree/Tuple.java b/mavibot/src/main/java/org/apache/directory/mavibot/btree/Tuple.java
index 93246c8..cde15ab 100644
--- a/mavibot/src/main/java/org/apache/directory/mavibot/btree/Tuple.java
+++ b/mavibot/src/main/java/org/apache/directory/mavibot/btree/Tuple.java
@@ -32,10 +32,10 @@
 public class Tuple<K, V>
 {
     /** The key */
-    private K key;
+    protected K key;
 
     /** The value */
-    private V value;
+    protected V value;
 
 
     /**