diff --git a/include/hpp/manipulation/graph/graph.hh b/include/hpp/manipulation/graph/graph.hh
index 0fc6144c6e506ba7df401ec07fd5b8dc1b039b6b..2fa1ee258eb3fac76f29d5d2c5642da7e3aefac0 100644
--- a/include/hpp/manipulation/graph/graph.hh
+++ b/include/hpp/manipulation/graph/graph.hh
@@ -45,27 +45,27 @@ namespace hpp {
           NodeSelectorPtr_t createNodeSelector();
 
           /// Returns the states of a configuration.
-          virtual Nodes_t getNode(const Configuration_t config);
+          Nodes_t getNode(const Configuration_t config) const;
 
           /// Select randomly outgoing edges of the given nodes.
-          virtual Edges_t chooseEdge(const Nodes_t& node);
+          Edges_t chooseEdge(const Nodes_t& node) const;
 
           /// Constraint to project onto the Nodes_t.
           /// \param the Nodes_t on which to project.
           /// \return The initialized projector.
-          virtual ConstraintSetPtr_t configConstraint (const Nodes_t& nodes);
+          ConstraintSetPtr_t configConstraint (const Nodes_t& nodes);
 
           /// Constraint to project onto the same leaf as config.
           /// \param edges a list of edges defining the foliation.
           /// \param config Configuration that will initialize the projector.
           /// \return The initialized projector.
-          virtual ConstraintSetPtr_t configConstraint (const Edges_t& edges, ConfigurationIn_t config);
+          ConstraintSetPtr_t configConstraint (const Edges_t& edges, ConfigurationIn_t config);
 
           /// Constraint to project a path.
           /// \param edges a list of edges defining the foliation.
           /// \param config Configuration that will initialize the constraint.
           /// \return The initialized constraint.
-          virtual ConstraintSetPtr_t pathConstraint (const Edges_t& edges, ConfigurationIn_t config);
+          ConstraintSetPtr_t pathConstraint (const Edges_t& edges, ConfigurationIn_t config);
 
           /// Return the NodeSelector with the given name if any,
           /// NULL pointer if not found.
diff --git a/include/hpp/manipulation/graph/node-selector.hh b/include/hpp/manipulation/graph/node-selector.hh
index df4144c241ba7f625afdc88fae1c8be046c24cb0..bbe446235432ff4ca6bf9e37ea1f2593006efb55 100644
--- a/include/hpp/manipulation/graph/node-selector.hh
+++ b/include/hpp/manipulation/graph/node-selector.hh
@@ -37,22 +37,22 @@ namespace hpp {
           NodePtr_t createNode ();
 
           /// Returns the state of a configuration.
-          virtual NodePtr_t getNode(const Configuration_t config);
+          NodePtr_t getNode(const Configuration_t config) const;
 
           /// Select randomly an outgoing edge of the given node.
-          virtual EdgePtr_t chooseEdge(const NodePtr_t& node);
+          virtual EdgePtr_t chooseEdge(const NodePtr_t& node) const;
 
           /// Print the object in a stream.
           std::ostream& print (std::ostream& os) const;
 
           /// Should never be called.
-          virtual void addNumericalConstraint (const core::DifferentiableFunctionPtr_t& /* function */)
+          void addNumericalConstraint (const core::DifferentiableFunctionPtr_t& /* function */)
           {
             HPP_THROW_EXCEPTION (Bad_function_call, "This component does not have constraints.");
           }
 
           /// Should never be called.
-          virtual void addLockedDofConstraint (const core::LockedDof& /* constraint */)
+          void addLockedDofConstraint (const core::LockedDof& /* constraint */)
           {
             HPP_THROW_EXCEPTION (Bad_function_call, "This component does not have constraints.");
           }
diff --git a/include/hpp/manipulation/graph/node.hh b/include/hpp/manipulation/graph/node.hh
index 32784f41da02d9666e68b480e2ca69b8ae01658e..db5b24b501b76871969c4874c3e339c8d476fb06 100644
--- a/include/hpp/manipulation/graph/node.hh
+++ b/include/hpp/manipulation/graph/node.hh
@@ -52,7 +52,7 @@ namespace hpp {
           virtual bool contains (const Configuration_t config);
 
           /// Get the parent NodeSelector.
-          NodeSelectorWkPtr_t nodeSelector ()
+          NodeSelectorWkPtr_t nodeSelector () const
           {
             return selector_;
           }
diff --git a/src/graph/graph.cc b/src/graph/graph.cc
index c64a4df216860b52488e58c1582f2ef0e19c2d8e..e61e28df8bcaf8a76f57e53d89f2d428eff4c941 100644
--- a/src/graph/graph.cc
+++ b/src/graph/graph.cc
@@ -73,16 +73,16 @@ namespace hpp {
         return robot_;
       }
 
-      Nodes_t Graph::getNode(const Configuration_t config)
+      Nodes_t Graph::getNode(const Configuration_t config) const
       {
         Nodes_t nodes;
-        for (NodeSelectors_t::iterator it = nodeSelectors_.begin();
+        for (NodeSelectors_t::const_iterator it = nodeSelectors_.begin();
             it != nodeSelectors_.end(); it++)
           nodes.push_back( (*it)->getNode(config) );
         return nodes;
       }
 
-      Edges_t Graph::chooseEdge(const Nodes_t& nodes)
+      Edges_t Graph::chooseEdge(const Nodes_t& nodes) const
       {
         Edges_t edges;
         for (Nodes_t::const_iterator it = nodes.begin();
diff --git a/src/graph/node-selector.cc b/src/graph/node-selector.cc
index 141bcd9189fa152b25e6b4ab239f0b95515dc46a..909ed6534221ce5f9794e93d3611ce5b2c00d3c1 100644
--- a/src/graph/node-selector.cc
+++ b/src/graph/node-selector.cc
@@ -44,16 +44,16 @@ namespace hpp {
         return newNode;
       }
 
-      NodePtr_t NodeSelector::getNode(const Configuration_t config)
+      NodePtr_t NodeSelector::getNode(const Configuration_t config) const
       {
-        for (Nodes_t::iterator it = orderedStates_.begin();
+        for (Nodes_t::const_iterator it = orderedStates_.begin();
             orderedStates_.end() != it; it++)
           if ((*it)->contains(config))
             return *it;
         return NodePtr_t ();
       }
 
-      EdgePtr_t NodeSelector::chooseEdge(const NodePtr_t& node)
+      EdgePtr_t NodeSelector::chooseEdge(const NodePtr_t& node) const
       {
         const Edges_t neighbors = node->neighbors();
         size_t n = rand() % neighbors.size();