diff --git a/exceptions/EmptyTreeException.java b/exceptions/EmptyTreeException.java
new file mode 100644
index 0000000..ea3aa34
--- /dev/null
+++ b/exceptions/EmptyTreeException.java
@@ -0,0 +1,17 @@
+package exceptions;
+
+/**
+ * Created with MONSTER.
+ * User: xgiovio
+ * Date: 05/03/14
+ * Time: 0.09
+ */
+public class EmptyTreeException extends RuntimeException {
+
+    public EmptyTreeException(){
+        super("Empty Tree");
+    }
+    public EmptyTreeException(String msg){
+        super(msg);
+    }
+}
diff --git a/tree/LinkedTree.java b/tree/LinkedTree.java
new file mode 100644
index 0000000..8163323
--- /dev/null
+++ b/tree/LinkedTree.java
@@ -0,0 +1,73 @@
+package tree;
+
+import exceptions.BoundaryViolationException;
+import exceptions.EmptyTreeException;
+import exceptions.InvalidPositionException;
+import position.Position;
+
+import java.util.Iterator;
+
+/**
+ * Created with xgiovio.macbookair.
+ * User: xgiovio
+ * Date: 07/04/14
+ * Time: 15:45
+ */
+public class LinkedTree <E> implements Tree<E> {
+
+
+    @Override
+    public int size() {
+        return 0;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return false;
+    }
+
+    @Override
+    public Iterable<Position<E>> positions() {
+        return null;
+    }
+
+    @Override
+    public E replace(Position<E> v, E e) throws InvalidPositionException {
+        return null;
+    }
+
+    @Override
+    public Position<E> root() throws EmptyTreeException {
+        return null;
+    }
+
+    @Override
+    public Position<E> parent(Position<E> v) throws InvalidPositionException, BoundaryViolationException {
+        return null;
+    }
+
+    @Override
+    public Iterable<Position<E>> children(Position<E> v) throws InvalidPositionException {
+        return null;
+    }
+
+    @Override
+    public boolean isInternal(Position<E> v) throws InvalidPositionException {
+        return false;
+    }
+
+    @Override
+    public boolean isExternal(Position<E> v) throws InvalidPositionException {
+        return false;
+    }
+
+    @Override
+    public boolean isRoot(Position<E> v) throws InvalidPositionException {
+        return false;
+    }
+
+    @Override
+    public Iterator<E> iterator() {
+        return null;
+    }
+}
diff --git a/tree/Tree.java b/tree/Tree.java
new file mode 100644
index 0000000..1805ae8
--- /dev/null
+++ b/tree/Tree.java
@@ -0,0 +1,33 @@
+package tree;
+
+import exceptions.BoundaryViolationException;
+import exceptions.EmptyTreeException;
+import exceptions.InvalidPositionException;
+import position.Position;
+
+import java.util.Iterator;
+
+/**
+ * Created with xgiovio.macbookair.
+ * User: xgiovio
+ * Date: 07/04/14
+ * Time: 15:17
+ */
+public interface Tree<E> extends Iterable<E> {
+
+
+    public int size();
+    public boolean isEmpty();
+
+    public Iterable<Position<E>> positions ();
+    public E replace (Position<E> v, E e) throws InvalidPositionException;
+    public Position<E> root () throws EmptyTreeException;
+    public Position<E> parent (Position <E> v) throws InvalidPositionException, BoundaryViolationException;
+    public Iterable <Position<E>> children (Position<E> v) throws InvalidPositionException; // anche se e' foglia
+
+    public boolean isInternal (Position<E> v) throws InvalidPositionException;
+    public boolean isExternal (Position<E> v) throws InvalidPositionException;
+    public boolean isRoot (Position <E> v) throws InvalidPositionException;
+
+
+}
diff --git a/tree/TreeNode.java b/tree/TreeNode.java
new file mode 100644
index 0000000..9c2c1d5
--- /dev/null
+++ b/tree/TreeNode.java
@@ -0,0 +1,55 @@
+package tree;
+
+import position.Position;
+import position.PositionList;
+
+/**
+ * Created with xgiovio.macbookair.
+ * User: xgiovio
+ * Date: 07/04/14
+ * Time: 15:30
+ */
+public class TreeNode<E> implements TreePosition<E> {
+
+    private E element = null;
+    private TreePosition<E> parent = null;
+    private PositionList<Position<E>> children= null;
+
+
+    public TreeNode(E in_element, TreePosition<E> in_parent, PositionList<Position<E>> in_children ){
+        element = in_element;
+        parent = in_parent;
+        children = in_children;
+    }
+
+
+    @Override
+    public void setElement(E o) {
+        element = o;
+    }
+
+    @Override
+    public PositionList<Position<E>> getChildren() {
+        return children;
+    }
+
+    @Override
+    public void setChildren(PositionList<Position<E>> c) {
+        children = c;
+    }
+
+    @Override
+    public TreePosition<E> getParent() {
+       return parent;
+    }
+
+    @Override
+    public void setParent(TreePosition<E> v) {
+      parent = v;
+    }
+
+    @Override
+    public E element() {
+        return element;
+    }
+}
diff --git a/tree/TreePosition.java b/tree/TreePosition.java
new file mode 100644
index 0000000..37695f1
--- /dev/null
+++ b/tree/TreePosition.java
@@ -0,0 +1,20 @@
+package tree;
+
+import position.Position;
+import position.PositionList;
+
+/**
+ * Created with xgiovio.macbookair.
+ * User: xgiovio
+ * Date: 07/04/14
+ * Time: 15:31
+ */
+public interface TreePosition<E> extends Position<E> {
+
+    public void setElement(E o);
+    public PositionList<Position<E>> getChildren ();
+    public void setChildren (PositionList<Position<E>> c);
+    public TreePosition<E> getParent();
+    public void setParent (TreePosition<E> v);
+
+}