diff --git a/src/Main.java b/src/Main.java
new file mode 100644
index 0000000..b66f1a3
--- /dev/null
+++ b/src/Main.java
@@ -0,0 +1,17 @@
+import expression.Expression;
+import expression.Tree;
+
+/**
+ * Created by xawirses on 29/03/17.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Expression e = new Expression();
+        e.negExpressionPrefixe();
+        System.out.println(e.getExpressionPrefixe());
+        System.out.println();
+
+        Tree treeExpression = new Tree(e.getExpressionPrefixe());
+        treeExpression.display();
+    }
+}
diff --git a/src/Node.java b/src/Node.java
deleted file mode 100644
index edd5e62..0000000
--- a/src/Node.java
+++ /dev/null
@@ -1,61 +0,0 @@
-/**
- * Created by azael on 20/03/17.
- */
-public class Node {
-
-    private char node;
-
-    private Node father;
-    private Node leftChild;
-    private Node rigthChild;
-    private int lvl;
-
-    private int pos = 0;
-
-    Node(Node father, Node leftChild, Node rightChild, char name, int lvl){
-        this.node = name;
-        this.father = father;
-        this.leftChild = leftChild;
-        this.rigthChild = rightChild;
-        this.lvl = lvl;
-    }
-
-    public void setLeftChild(Node leftChild) { this.leftChild = leftChild; }
-    public void setRigthChild(Node rigthChild) { this.rigthChild = rigthChild; }
-
-    public void setFather(Node father) {
-        this.father = father;
-    }
-
-    public void display() {
-        System.out.println(node);
-    }
-
-    public int getLvl() {
-        return lvl;
-    }
-
-    public Node getLeftChild() {
-        return leftChild;
-    }
-
-    public Node getRigthChild() {
-        return rigthChild;
-    }
-
-    public char getNode() {
-        return node;
-    }
-
-    public Node getFather() {
-        return father;
-    }
-
-    public int getPos() {
-        return pos;
-    }
-
-    public void setPos(int pos) {
-        this.pos = pos;
-    }
-}
diff --git a/src/Expression.java b/src/expression/Expression.java
similarity index 90%
rename from src/Expression.java
rename to src/expression/Expression.java
index a30b87d..fd39217 100644
--- a/src/Expression.java
+++ b/src/expression/Expression.java
@@ -1,3 +1,5 @@
+package expression;
+
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
@@ -102,10 +104,6 @@ public class Expression {
         expressionPrefixe = reverseExpression(reversePrefix);
     }
 
-    public String getExpression() {
-        return expression;
-    }
-
     public String getExpressionPrefixe() {
         return expressionPrefixe;
     }
@@ -113,14 +111,4 @@ public class Expression {
     public void negExpressionPrefixe (){
         expressionPrefixe = "!" + expressionPrefixe;
     }
-
-    public static void main(String[] args) {
-        Expression e = new Expression();
-        e.negExpressionPrefixe();
-        System.out.println(e.getExpressionPrefixe());
-        System.out.println();
-
-        Tree t = new Tree(e.getExpressionPrefixe());
-        t.display();
-    }
 }
diff --git a/src/expression/Node.java b/src/expression/Node.java
new file mode 100644
index 0000000..b9a7875
--- /dev/null
+++ b/src/expression/Node.java
@@ -0,0 +1,36 @@
+package expression;
+
+/**
+ * Created by azael on 20/03/17.
+ */
+public class Node {
+
+    private char node;
+
+    private Node leftChild;
+    private Node rigthChild;
+    private int lvl;
+
+    Node(Node leftChild, Node rightChild, char name, int lvl){
+        this.node = name;
+        this.leftChild = leftChild;
+        this.rigthChild = rightChild;
+        this.lvl = lvl;
+    }
+
+    public void display() {
+        System.out.println(node);
+    }
+
+    public int getLvl() {
+        return lvl;
+    }
+
+    public Node getLeftChild() {
+        return leftChild;
+    }
+
+    public Node getRigthChild() {
+        return rigthChild;
+    }
+}
diff --git a/src/Operator.java b/src/expression/Operator.java
similarity index 90%
rename from src/Operator.java
rename to src/expression/Operator.java
index a67a124..d0ff3f1 100644
--- a/src/Operator.java
+++ b/src/expression/Operator.java
@@ -1,3 +1,5 @@
+package expression;
+
 /**
  * Created by xawirses on 28/02/17.
  */
diff --git a/src/Tree.java b/src/expression/Tree.java
similarity index 67%
rename from src/Tree.java
rename to src/expression/Tree.java
index d90a95b..25cce97 100644
--- a/src/Tree.java
+++ b/src/expression/Tree.java
@@ -1,3 +1,7 @@
+package expression;
+
+import expression.Expression;
+
 /**
  * Created by azael on 20/03/17.
  */
@@ -6,7 +10,7 @@ public class Tree {
     private Node root;
     private String exp;
 
-    Tree (String exp){
+    public Tree(String exp){
         this.exp = exp;
         root = tree(0);
     }
@@ -17,22 +21,16 @@ public class Tree {
         if(Expression.isOperator(item)) {
             if (item == '!'){
                 Node fils = tree(pos+1);
-                Node f =  new Node(null, fils, null, item, 1+fils.getLvl());
-                fils.setPos(1);
-                fils.setFather(f);
+                Node f =  new Node(fils, null, item, 1+fils.getLvl());
                 return f;
             } else {
                 Node filsG = tree(pos+1);
                 Node filsD = tree(pos+filsG.getLvl()+1);
-                Node f = new Node(null, filsG, filsD, item, filsG.getLvl() + filsD.getLvl()+1);
-                filsG.setPos(1);
-                filsD.setPos(2);
-                filsG.setFather(f);
-                filsD.setFather(f);
+                Node f = new Node(filsG, filsD, item, filsG.getLvl() + filsD.getLvl()+1);
                 return f;
             }
         } else {
-            return new Node(null, null, null, item, 1);
+            return new Node(null, null, item, 1);
         }
     }
 
diff --git a/src/statement/World.java b/src/statement/World.java
new file mode 100644
index 0000000..933b54d
--- /dev/null
+++ b/src/statement/World.java
@@ -0,0 +1,19 @@
+package statement;
+
+import expression.Node;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+/**
+ * Created by xawirses on 29/03/17.
+ */
+public class World {
+    private String name;
+    private Collection<Node> expressions = new ArrayList<>();
+    private Collection<World> involved = new ArrayList<>();
+
+    public World(String name) {
+        this.name = name;
+    }
+}