diff --git a/vlsisapd/doc/openChams/Layout.dox b/vlsisapd/doc/openChams/Layout.dox
index a5d1741f..f1467a37 100644
--- a/vlsisapd/doc/openChams/Layout.dox
+++ b/vlsisapd/doc/openChams/Layout.dox
@@ -30,5 +30,16 @@ namespace OpenChams {
 /*! \fn inline const std::map<Name, Infos*>& Layout::getInstances()
  *   \brief returns the map of Instances.
  */
+
+/*! \fn inline Node* Layout::getHBTreeRoot()
+ *   \brief returns the root of the placement tree associated to the layout.
+ */
+
+/*! \fn inline void  Layout::setHBTreeRoot(Node* root)
+ *   \brief sets the root of the placement tree associated to the layout.
+ *
+ *   \param root the root of the palcement tree.
+ */
+
 }
 
diff --git a/vlsisapd/doc/openChams/Node.dox b/vlsisapd/doc/openChams/Node.dox
new file mode 100644
index 00000000..f0d6f048
--- /dev/null
+++ b/vlsisapd/doc/openChams/Node.dox
@@ -0,0 +1,107 @@
+// -*- C++ -*-
+
+namespace OpenChams {
+/*! \class Node
+ *
+ *  This class describes a node of the placement tree.
+ *
+ *  This is an abstract class used to easily managed blocs and groups of the placement tree.
+ */
+
+/*! \fn inline Name Node::getName()
+ *   \brief returns the name of the node.
+ */
+
+/*! \fn inline Position Node::getPosition()
+ *   \brief returns the position of the node.
+ */
+
+/*! \fn inline Node* Node::getParent()
+ *   \brief returns the parent node of the current node.
+ */
+
+/*! \fn inline Node* Node::getRight()
+ *   \brief returns the child node at the right of the current node.
+ */
+
+/*! \fn inline Node* Node::getTop()
+ *   \brief returns the child node at the top of the current node.
+ */
+
+/*! \fn inline bool Node::isRoot()
+ *   \brief returns tru if the node is the root of the tree (has no parent).
+ */
+
+/*! \fn inline void Node::setRight(Node* node)
+ *   \brief sets the child node at the right of the current node.
+ *
+ *   \param node the node at the right of the current node.
+ */
+
+/*! \fn inline void Node::setTop(Node* node)
+ *   \brief sets the node at the top of the current node.
+ *
+ *   \param node the node at the top of the current node.
+ */
+
+
+/*! \class Bloc
+ *
+ *  This class describes a bloc of the placement tree.
+ */
+
+/*! \fn Bloc::Bloc(Name blocName, Position position, Node* parent)
+ *   \brief creates a new bloc.
+ *
+ *   \param blocName the name of the bloc
+ *   \param position the position of the bloc (default value: NONE)
+ *   \param parent   the parent node of the node (default value: NULL)
+ */
+
+
+/*! \class Group
+ *
+ *  This class describes a group of the placement tree.
+ */
+
+/*! \fn inline void Group::setRootNode(Node* node)
+ *   \brief sets the root node of the group.
+ *
+ *   \param node the root node of the group
+ */
+
+/*! \fn inline void Group::setIsolated(bool isolated)
+ *   \brief sets whether the group has an isolation constraint or not.
+ *
+ *   \param isolated if true the group has an isolation constraint.
+ */
+
+/*! \fn inline void Group::setPaired(bool paired)
+ *   \brief sets whether the group has a pairing constraint or not.
+ *
+ *   \param paired if true the group has a pairing constraint.
+ */
+
+/*! \fn inline void Group::setAlign(Align align)
+ *   \brief sets an alignment constraint on the group.
+ *
+ *   \param align the value of the alignment constraint can be NONE, VERTICAL or HORIZONTAL.
+ */
+
+/*! \fn inline Node* group::getRootNode()
+ *   \brief returns the root node of the group.
+ */
+
+/*! \fn inline bool Group::isIsolated()
+ *   \brief returns true if the group has an isolation constraint.
+ */
+
+/*! \fn inline bool Group::isPaired()
+ *   \brief returns true if the group has a pairing constraint.
+ */
+
+/*! \fn inline Align Group::getAlign()
+ *   \brief returns the alignment constraint of the group.
+ */
+
+}
diff --git a/vlsisapd/doc/openChams/openChams.dox b/vlsisapd/doc/openChams/openChams.dox
index 1d80604c..a6fddef6 100644
--- a/vlsisapd/doc/openChams/openChams.dox
+++ b/vlsisapd/doc/openChams/openChams.dox
@@ -35,6 +35,9 @@
     - OpenChams::IntermediatePoint
   - Layout
     - OpenChams::Layout
+    - OpenChams::Node
+    - OpenChams::Bloc
+    - OpenChams::Group
 
   \subsection openChamsParser Using the parser
   Simply load an OPENCHAMS file using the static function OpenChams::Circuit::readFromFile() and then get the netlist object (OpenChams::Circuit::getNetlist()) or the sizing procedure (OpenChams::Circuit::getSizing(), might be NULL) or any other useful information (see OpenChams::Circuit).