diff -r f2ea4aac9ada -r c94ef40a22ce src/lemon/skeletons/graph.h
--- a/src/lemon/skeletons/graph.h	Mon Oct 25 13:29:46 2004 +0000
+++ b/src/lemon/skeletons/graph.h	Wed Oct 27 22:38:50 2004 +0000
@@ -23,6 +23,8 @@
 
 #include <lemon/invalid.h>
 #include <lemon/skeletons/maps.h>
+#include <lemon/concept_check.h>
+#include <lemon/skeletons/graph_component.h>
 
 namespace lemon {
   namespace skeleton {
@@ -30,734 +32,883 @@
     /// \addtogroup skeletons
     /// @{
 
-    /// An empty static graph class.
+//     /// An empty static graph class.
   
-    /// This class provides all the common features of a graph structure,
-    /// however completely without implementations and real data structures
-    /// behind the interface.
-    /// All graph algorithms should compile with this class, but it will not
-    /// run properly, of course.
-    ///
-    /// It can be used for checking the interface compatibility,
-    /// or it can serve as a skeleton of a new graph structure.
-    /// 
-    /// Also, you will find here the full documentation of a certain graph
-    /// feature, the documentation of a real graph imlementation
-    /// like @ref ListGraph or
-    /// @ref SmartGraph will just refer to this structure.
-    ///
-    /// \todo A pages describing the concept of concept description would
-    /// be nice.
-    class StaticGraph
-    {
+//     /// This class provides all the common features of a graph structure,
+//     /// however completely without implementations and real data structures
+//     /// behind the interface.
+//     /// All graph algorithms should compile with this class, but it will not
+//     /// run properly, of course.
+//     ///
+//     /// It can be used for checking the interface compatibility,
+//     /// or it can serve as a skeleton of a new graph structure.
+//     /// 
+//     /// Also, you will find here the full documentation of a certain graph
+//     /// feature, the documentation of a real graph imlementation
+//     /// like @ref ListGraph or
+//     /// @ref SmartGraph will just refer to this structure.
+//     ///
+//     /// \todo A pages describing the concept of concept description would
+//     /// be nice.
+//     class StaticGraph
+//     {
+//     public:
+//       /// Defalult constructor.
+
+//       /// Defalult constructor.
+//       ///
+//       StaticGraph() { }
+//       ///Copy consructor.
+
+// //       ///\todo It is not clear, what we expect from a copy constructor.
+// //       ///E.g. How to assign the nodes/edges to each other? What about maps?
+// //       StaticGraph(const StaticGraph& g) { }
+
+//       /// The base type of node iterators, 
+//       /// or in other words, the trivial node iterator.
+
+//       /// This is the base type of each node iterator,
+//       /// thus each kind of node iterator converts to this.
+//       /// More precisely each kind of node iterator should be inherited 
+//       /// from the trivial node iterator.
+//       class Node {
+//       public:
+// 	/// Default constructor
+
+// 	/// @warning The default constructor sets the iterator
+// 	/// to an undefined value.
+// 	Node() { }
+// 	/// Copy constructor.
+
+// 	/// Copy constructor.
+// 	///
+// 	Node(const Node&) { }
+
+// 	/// Invalid constructor \& conversion.
+
+// 	/// This constructor initializes the iterator to be invalid.
+// 	/// \sa Invalid for more details.
+// 	Node(Invalid) { }
+// 	/// Equality operator
+
+// 	/// Two iterators are equal if and only if they point to the
+// 	/// same object or both are invalid.
+// 	bool operator==(Node) const { return true; }
+
+// 	/// Inequality operator
+	
+// 	/// \sa operator==(Node n)
+// 	///
+// 	bool operator!=(Node) const { return true; }
+
+//  	///Comparison operator.
+
+// 	///This is a strict ordering between the nodes.
+// 	///
+// 	///This ordering can be different from the order in which NodeIt
+// 	///goes through the nodes.
+// 	///\todo Possibly we don't need it.
+// 	bool operator<(Node) const { return true; }
+//       };
+    
+//       /// This iterator goes through each node.
+
+//       /// This iterator goes through each node.
+//       /// Its usage is quite simple, for example you can count the number
+//       /// of nodes in graph \c g of type \c Graph like this:
+//       /// \code
+//       /// int count=0;
+//       /// for (Graph::NodeIt n(g); n!=INVALID ++n) ++count;
+//       /// \endcode
+//       class NodeIt : public Node {
+//       public:
+// 	/// Default constructor
+
+// 	/// @warning The default constructor sets the iterator
+// 	/// to an undefined value.
+// 	NodeIt() { }
+// 	/// Copy constructor.
+	
+// 	/// Copy constructor.
+// 	///
+// 	NodeIt(const NodeIt&) { }
+// 	/// Invalid constructor \& conversion.
+
+// 	/// Initialize the iterator to be invalid.
+// 	/// \sa Invalid for more details.
+// 	NodeIt(Invalid) { }
+// 	/// Sets the iterator to the first node.
+
+// 	/// Sets the iterator to the first node of \c g.
+// 	///
+// 	NodeIt(const StaticGraph& g) { }
+// 	/// Node -> NodeIt conversion.
+
+// 	/// Sets the iterator to the node of \c g pointed by the trivial 
+// 	/// iterator n.
+// 	/// This feature necessitates that each time we 
+// 	/// iterate the edge-set, the iteration order is the same.
+// 	NodeIt(const StaticGraph& g, const Node& n) { }
+// 	/// Next node.
+
+// 	/// Assign the iterator to the next node.
+// 	///
+// 	NodeIt& operator++() { return *this; }
+//       };
+    
+    
+//       /// The base type of the edge iterators.
+
+//       /// The base type of the edge iterators.
+//       ///
+//       class Edge {
+//       public:
+// 	/// Default constructor
+
+// 	/// @warning The default constructor sets the iterator
+// 	/// to an undefined value.
+// 	Edge() { }
+// 	/// Copy constructor.
+
+// 	/// Copy constructor.
+// 	///
+// 	Edge(const Edge&) { }
+// 	/// Initialize the iterator to be invalid.
+
+// 	/// Initialize the iterator to be invalid.
+// 	///
+// 	Edge(Invalid) { }
+// 	/// Equality operator
+
+// 	/// Two iterators are equal if and only if they point to the
+// 	/// same object or both are invalid.
+// 	bool operator==(Edge) const { return true; }
+// 	/// Inequality operator
+
+// 	/// \sa operator==(Node n)
+// 	///
+// 	bool operator!=(Edge) const { return true; }
+//  	///Comparison operator.
+
+// 	///This is a strict ordering between the nodes.
+// 	///
+// 	///This ordering can be different from the order in which NodeIt
+// 	///goes through the nodes.
+// 	///\todo Possibly we don't need it.
+//  	bool operator<(Edge) const { return true; }
+//       };
+    
+//       /// This iterator goes trough the outgoing edges of a node.
+
+//       /// This iterator goes trough the \e outgoing edges of a certain node
+//       /// of a graph.
+//       /// Its usage is quite simple, for example you can count the number
+//       /// of outgoing edges of a node \c n
+//       /// in graph \c g of type \c Graph as follows.
+//       /// \code
+//       /// int count=0;
+//       /// for (Graph::OutEdgeIt e(g, n); e!=INVALID; ++e) ++count;
+//       /// \endcode
+    
+//       class OutEdgeIt : public Edge {
+//       public:
+// 	/// Default constructor
+
+// 	/// @warning The default constructor sets the iterator
+// 	/// to an undefined value.
+// 	OutEdgeIt() { }
+// 	/// Copy constructor.
+
+// 	/// Copy constructor.
+// 	///
+// 	OutEdgeIt(const OutEdgeIt&) { }
+// 	/// Initialize the iterator to be invalid.
+
+// 	/// Initialize the iterator to be invalid.
+// 	///
+// 	OutEdgeIt(Invalid) { }
+// 	/// This constructor sets the iterator to first outgoing edge.
+    
+// 	/// This constructor set the iterator to the first outgoing edge of
+// 	/// node
+// 	///@param n the node
+// 	///@param g the graph
+// 	OutEdgeIt(const StaticGraph& g, const Node& n) { }
+// 	/// Edge -> OutEdgeIt conversion
+
+// 	/// Sets the iterator to the value of the trivial iterator \c e.
+// 	/// This feature necessitates that each time we 
+// 	/// iterate the edge-set, the iteration order is the same.
+// 	OutEdgeIt(const StaticGraph& g, const Edge& e) { }
+// 	///Next outgoing edge
+	
+// 	/// Assign the iterator to the next 
+// 	/// outgoing edge of the corresponding node.
+// 	OutEdgeIt& operator++() { return *this; }
+//       };
+
+//       /// This iterator goes trough the incoming edges of a node.
+
+//       /// This iterator goes trough the \e incoming edges of a certain node
+//       /// of a graph.
+//       /// Its usage is quite simple, for example you can count the number
+//       /// of outgoing edges of a node \c n
+//       /// in graph \c g of type \c Graph as follows.
+//       /// \code
+//       /// int count=0;
+//       /// for(Graph::InEdgeIt e(g, n); e!=INVALID; ++e) ++count;
+//       /// \endcode
+
+//       class InEdgeIt : public Edge {
+//       public:
+// 	/// Default constructor
+
+// 	/// @warning The default constructor sets the iterator
+// 	/// to an undefined value.
+// 	InEdgeIt() { }
+// 	/// Copy constructor.
+
+// 	/// Copy constructor.
+// 	///
+// 	InEdgeIt(const InEdgeIt&) { }
+// 	/// Initialize the iterator to be invalid.
+
+// 	/// Initialize the iterator to be invalid.
+// 	///
+// 	InEdgeIt(Invalid) { }
+// 	/// This constructor sets the iterator to first incoming edge.
+    
+// 	/// This constructor set the iterator to the first incoming edge of
+// 	/// node
+// 	///@param n the node
+// 	///@param g the graph
+// 	InEdgeIt(const StaticGraph& g, const Node& n) { }
+// 	/// Edge -> InEdgeIt conversion
+
+// 	/// Sets the iterator to the value of the trivial iterator \c e.
+// 	/// This feature necessitates that each time we 
+// 	/// iterate the edge-set, the iteration order is the same.
+// 	InEdgeIt(const StaticGraph& g, const Edge& n) { }
+// 	/// Next incoming edge
+
+// 	/// Assign the iterator to the next inedge of the corresponding node.
+// 	///
+// 	InEdgeIt& operator++() { return *this; }
+//       };
+//       /// This iterator goes through each edge.
+
+//       /// This iterator goes through each edge of a graph.
+//       /// Its usage is quite simple, for example you can count the number
+//       /// of edges in a graph \c g of type \c Graph as follows:
+//       /// \code
+//       /// int count=0;
+//       /// for(Graph::EdgeIt e(g); e!=INVALID; ++e) ++count;
+//       /// \endcode
+//       class EdgeIt : public Edge {
+//       public:
+// 	/// Default constructor
+
+// 	/// @warning The default constructor sets the iterator
+// 	/// to an undefined value.
+// 	EdgeIt() { }
+// 	/// Copy constructor.
+
+// 	/// Copy constructor.
+// 	///
+// 	EdgeIt(const EdgeIt&) { }
+// 	/// Initialize the iterator to be invalid.
+
+// 	/// Initialize the iterator to be invalid.
+// 	///
+// 	EdgeIt(Invalid) { }
+// 	/// This constructor sets the iterator to first edge.
+    
+// 	/// This constructor set the iterator to the first edge of
+// 	/// node
+// 	///@param g the graph
+// 	EdgeIt(const StaticGraph& g) { }
+// 	/// Edge -> EdgeIt conversion
+
+// 	/// Sets the iterator to the value of the trivial iterator \c e.
+// 	/// This feature necessitates that each time we 
+// 	/// iterate the edge-set, the iteration order is the same.
+// 	EdgeIt(const StaticGraph&, const Edge&) { } 
+//     	///Next edge
+	
+// 	/// Assign the iterator to the next 
+// 	/// edge of the corresponding node.
+// 	EdgeIt& operator++() { return *this; }
+//       };
+
+//       /// First node of the graph.
+
+//       /// \retval i the first node.
+//       /// \return the first node.
+//       ///
+//       NodeIt& first(NodeIt& i) const { return i; }
+
+//       /// The first incoming edge.
+
+//       /// The first incoming edge.
+//       ///
+//       InEdgeIt& first(InEdgeIt &i, Node) const { return i; }
+//       /// The first outgoing edge.
+
+//       /// The first outgoing edge.
+//       ///
+//       OutEdgeIt& first(OutEdgeIt& i, Node) const { return i; }
+//       /// The first edge of the Graph.
+
+//       /// The first edge of the Graph.
+//       ///
+//       EdgeIt& first(EdgeIt& i) const { return i; }
+
+//       ///Gives back the head node of an edge.
+
+//       ///Gives back the head node of an edge.
+//       ///
+//       Node head(Edge) const { return INVALID; }
+//       ///Gives back the tail node of an edge.
+
+//       ///Gives back the tail node of an edge.
+//       ///
+//       Node tail(Edge) const { return INVALID; }
+  
+//       ///Gives back the \e id of a node.
+
+//       ///\warning Not all graph structures provide this feature.
+//       ///
+//       ///\todo Should each graph provide \c id?
+//       int id(const Node&) const { return 0; }
+//       ///Gives back the \e id of an edge.
+
+//       ///\warning Not all graph structures provide this feature.
+//       ///
+//       ///\todo Should each graph provide \c id?
+//       int id(const Edge&) const { return 0; }
+
+//       ///\e
+      
+//       ///\todo Should it be in the concept?
+//       ///
+//       int nodeNum() const { return 0; }
+//       ///\e
+
+//       ///\todo Should it be in the concept?
+//       ///
+//       int edgeNum() const { return 0; }
+
+
+//       ///Reference map of the nodes to type \c T.
+
+//       /// \ingroup skeletons
+//       ///Reference map of the nodes to type \c T.
+//       /// \sa Reference
+//       /// \warning Making maps that can handle bool type (NodeMap<bool>)
+//       /// needs some extra attention!
+//       template<class T> class NodeMap : public ReferenceMap< Node, T >
+//       {
+//       public:
+
+// 	///\e
+// 	NodeMap(const StaticGraph&) { }
+// 	///\e
+// 	NodeMap(const StaticGraph&, T) { }
+
+// 	///Copy constructor
+// 	template<typename TT> NodeMap(const NodeMap<TT>&) { }
+// 	///Assignment operator
+// 	template<typename TT> NodeMap& operator=(const NodeMap<TT>&)
+// 	{ return *this; }
+//       };
+
+//       ///Reference map of the edges to type \c T.
+
+//       /// \ingroup skeletons
+//       ///Reference map of the edges to type \c T.
+//       /// \sa Reference
+//       /// \warning Making maps that can handle bool type (EdgeMap<bool>)
+//       /// needs some extra attention!
+//       template<class T> class EdgeMap
+// 	: public ReferenceMap<Edge,T>
+//       {
+//       public:
+
+// 	///\e
+// 	EdgeMap(const StaticGraph&) { }
+// 	///\e
+// 	EdgeMap(const StaticGraph&, T) { }
+    
+// 	///Copy constructor
+// 	template<typename TT> EdgeMap(const EdgeMap<TT>&) { }
+// 	///Assignment operator
+// 	template<typename TT> EdgeMap &operator=(const EdgeMap<TT>&)
+// 	{ return *this; }
+//       };
+//     };
+
+//     struct DummyType {
+//       int value;
+//       DummyType() {}
+//       DummyType(int p) : value(p) {}
+//       DummyType& operator=(int p) { value = p; return *this;}
+//     };
+    
+//     ///\brief Checks whether \c G meets the
+//     ///\ref lemon::skeleton::StaticGraph "StaticGraph" concept
+//     template<class Graph> void checkCompileStaticGraph(Graph &G) 
+//     {
+//       typedef typename Graph::Node Node;
+//       typedef typename Graph::NodeIt NodeIt;
+//       typedef typename Graph::Edge Edge;
+//       typedef typename Graph::EdgeIt EdgeIt;
+//       typedef typename Graph::InEdgeIt InEdgeIt;
+//       typedef typename Graph::OutEdgeIt OutEdgeIt;
+  
+//       {
+// 	Node i; Node j(i); Node k(INVALID);
+// 	i=j;
+// 	bool b; b=true;
+// 	b=(i==INVALID); b=(i!=INVALID);
+// 	b=(i==j); b=(i!=j); b=(i<j);
+//       }
+//       {
+// 	NodeIt i; NodeIt j(i); NodeIt k(INVALID); NodeIt l(G);
+// 	i=j;
+// 	j=G.first(i);
+// 	j=++i;
+// 	bool b; b=true;
+// 	b=(i==INVALID); b=(i!=INVALID);
+// 	Node n(i);
+// 	n=i;
+// 	b=(i==j); b=(i!=j); b=(i<j);
+// 	//Node ->NodeIt conversion
+// 	NodeIt ni(G,n);
+//       }
+//       {
+// 	Edge i; Edge j(i); Edge k(INVALID);
+// 	i=j;
+// 	bool b; b=true;
+// 	b=(i==INVALID); b=(i!=INVALID);
+// 	b=(i==j); b=(i!=j); b=(i<j);
+//       }
+//       {
+// 	EdgeIt i; EdgeIt j(i); EdgeIt k(INVALID); EdgeIt l(G);
+// 	i=j;
+// 	j=G.first(i);
+// 	j=++i;
+// 	bool b; b=true;
+// 	b=(i==INVALID); b=(i!=INVALID);
+// 	Edge e(i);
+// 	e=i;
+// 	b=(i==j); b=(i!=j); b=(i<j);
+// 	//Edge ->EdgeIt conversion
+// 	EdgeIt ei(G,e);
+//       }
+//       {
+// 	Node n;
+// 	InEdgeIt i; InEdgeIt j(i); InEdgeIt k(INVALID); InEdgeIt l(G,n);
+// 	i=j;
+// 	j=G.first(i,n);
+// 	j=++i;
+// 	bool b; b=true;
+// 	b=(i==INVALID); b=(i!=INVALID);
+// 	Edge e(i);
+// 	e=i;
+// 	b=(i==j); b=(i!=j); b=(i<j);
+// 	//Edge ->InEdgeIt conversion
+// 	InEdgeIt ei(G,e);
+//       }
+//       {
+// 	Node n;
+// 	OutEdgeIt i; OutEdgeIt j(i); OutEdgeIt k(INVALID); OutEdgeIt l(G,n);
+// 	i=j;
+// 	j=G.first(i,n);
+// 	j=++i;
+// 	bool b; b=true;
+// 	b=(i==INVALID); b=(i!=INVALID);
+// 	Edge e(i);
+// 	e=i;
+// 	b=(i==j); b=(i!=j); b=(i<j);
+// 	//Edge ->OutEdgeIt conversion
+// 	OutEdgeIt ei(G,e);
+//       }
+//       {
+// 	Node n,m;
+// 	n=m=INVALID;
+// 	Edge e;
+// 	e=INVALID;
+// 	n=G.tail(e);
+// 	n=G.head(e);
+//       }
+//       // id tests
+//       { Node n; int i=G.id(n); i=i; }
+//       { Edge e; int i=G.id(e); i=i; }
+//       //NodeMap tests
+//       {
+// 	Node k;
+// 	typename Graph::template NodeMap<int> m(G);
+// 	//Const map
+// 	typename Graph::template NodeMap<int> const &cm = m;
+// 	//Inicialize with default value
+// 	typename Graph::template NodeMap<int> mdef(G,12);
+// 	//Copy
+// 	typename Graph::template NodeMap<int> mm(cm);
+// 	//Copy from another type
+// 	typename Graph::template NodeMap<double> dm(cm);
+// 	//Copy to more complex type
+// 	typename Graph::template NodeMap<DummyType> em(cm);
+// 	int v;
+// 	v=m[k]; m[k]=v; m.set(k,v);
+// 	v=cm[k];
+    
+// 	m=cm;  
+// 	dm=cm; //Copy from another type  
+// 	em=cm; //Copy to more complex type
+// 	{
+// 	  //Check the typedef's
+// 	  typename Graph::template NodeMap<int>::ValueType val;
+// 	  val=1;
+// 	  typename Graph::template NodeMap<int>::KeyType key;
+// 	  key = typename Graph::NodeIt(G);
+// 	}
+//       }  
+//       { //bool NodeMap
+// 	Node k;
+// 	typename Graph::template NodeMap<bool> m(G);
+// 	typename Graph::template NodeMap<bool> const &cm = m;  //Const map
+// 	//Inicialize with default value
+// 	typename Graph::template NodeMap<bool> mdef(G,12);
+// 	typename Graph::template NodeMap<bool> mm(cm);   //Copy
+// 	typename Graph::template NodeMap<int> dm(cm); //Copy from another type
+// 	bool v;
+// 	v=m[k]; m[k]=v; m.set(k,v);
+// 	v=cm[k];
+    
+// 	m=cm;  
+// 	dm=cm; //Copy from another type
+// 	m=dm; //Copy to another type
+
+// 	{
+// 	  //Check the typedef's
+// 	  typename Graph::template NodeMap<bool>::ValueType val;
+// 	  val=true;
+// 	  typename Graph::template NodeMap<bool>::KeyType key;
+// 	  key= typename Graph::NodeIt(G);
+// 	}
+//       }
+//       //EdgeMap tests
+//       {
+// 	Edge k;
+// 	typename Graph::template EdgeMap<int> m(G);
+// 	typename Graph::template EdgeMap<int> const &cm = m;  //Const map
+// 	//Inicialize with default value
+// 	typename Graph::template EdgeMap<int> mdef(G,12);
+// 	typename Graph::template EdgeMap<int> mm(cm);   //Copy
+// 	typename Graph::template EdgeMap<double> dm(cm);//Copy from another type
+// 	int v;
+// 	v=m[k]; m[k]=v; m.set(k,v);
+// 	v=cm[k];
+    
+// 	m=cm;  
+// 	dm=cm; //Copy from another type
+// 	{
+// 	  //Check the typedef's
+// 	  typename Graph::template EdgeMap<int>::ValueType val;
+// 	  val=1;
+// 	  typename Graph::template EdgeMap<int>::KeyType key;
+// 	  key= typename Graph::EdgeIt(G);
+// 	}
+//       }  
+//       { //bool EdgeMap
+// 	Edge k;
+// 	typename Graph::template EdgeMap<bool> m(G);
+// 	typename Graph::template EdgeMap<bool> const &cm = m;  //Const map
+// 	//Inicialize with default value
+// 	typename Graph::template EdgeMap<bool> mdef(G,12);
+// 	typename Graph::template EdgeMap<bool> mm(cm);   //Copy
+// 	typename Graph::template EdgeMap<int> dm(cm); //Copy from another type
+// 	bool v;
+// 	v=m[k]; m[k]=v; m.set(k,v);
+// 	v=cm[k];
+    
+// 	m=cm;  
+// 	dm=cm; //Copy from another type
+// 	m=dm; //Copy to another type
+// 	{
+// 	  //Check the typedef's
+// 	  typename Graph::template EdgeMap<bool>::ValueType val;
+// 	  val=true;
+// 	  typename Graph::template EdgeMap<bool>::KeyType key;
+// 	  key= typename Graph::EdgeIt(G);
+// 	}
+//       }
+//     }
+    
+//     /// An empty non-static graph class.
+    
+//     /// This class provides everything that \ref StaticGraph
+//     /// with additional functionality which enables to build a
+//     /// graph from scratch.
+//     class ExtendableGraph : public StaticGraph
+//     {
+//     public:
+//       /// Defalult constructor.
+
+//       /// Defalult constructor.
+//       ///
+//       ExtendableGraph() { }
+//       ///Add a new node to the graph.
+
+//       /// \return the new node.
+//       ///
+//       Node addNode() { return INVALID; }
+//       ///Add a new edge to the graph.
+
+//       ///Add a new edge to the graph with tail node \c t
+//       ///and head node \c h.
+//       ///\return the new edge.
+//       Edge addEdge(Node h, Node t) { return INVALID; }
+    
+//       /// Resets the graph.
+
+//       /// This function deletes all edges and nodes of the graph.
+//       /// It also frees the memory allocated to store them.
+//       /// \todo It might belong to \ref ErasableGraph.
+//       void clear() { }
+//     };
+
+    
+//     ///\brief Checks whether \c G meets the
+//     ///\ref lemon::skeleton::ExtendableGraph "ExtendableGraph" concept
+//     template<class Graph> void checkCompileExtendableGraph(Graph &G) 
+//     {
+//       checkCompileStaticGraph(G);
+
+//       typedef typename Graph::Node Node;
+//       typedef typename Graph::NodeIt NodeIt;
+//       typedef typename Graph::Edge Edge;
+//       typedef typename Graph::EdgeIt EdgeIt;
+//       typedef typename Graph::InEdgeIt InEdgeIt;
+//       typedef typename Graph::OutEdgeIt OutEdgeIt;
+  
+//       Node n,m;
+//       n=G.addNode();
+//       m=G.addNode();
+//       Edge e;
+//       e=G.addEdge(n,m); 
+  
+//       //  G.clear();
+//     }
+
+
+//     /// An empty erasable graph class.
+  
+//     /// This class is an extension of \ref ExtendableGraph. It also makes it
+//     /// possible to erase edges or nodes.
+//     class ErasableGraph : public ExtendableGraph
+//     {
+//     public:
+//       /// Defalult constructor.
+
+//       /// Defalult constructor.
+//       ///
+//       ErasableGraph() { }
+//       /// Deletes a node.
+
+//       /// Deletes node \c n node.
+//       ///
+//       void erase(Node n) { }
+//       /// Deletes an edge.
+
+//       /// Deletes edge \c e edge.
+//       ///
+//       void erase(Edge e) { }
+//     };
+    
+//     template<class Graph> void checkCompileGraphEraseEdge(Graph &G) 
+//     {
+//       typename Graph::Edge e;
+//       G.erase(e);
+//     }
+
+//     template<class Graph> void checkCompileGraphEraseNode(Graph &G) 
+//     {
+//       typename Graph::Node n;
+//       G.erase(n);
+//     }
+
+//     ///\brief Checks whether \c G meets the
+//     ///\ref lemon::skeleton::EresableGraph "EresableGraph" concept
+//     template<class Graph> void checkCompileErasableGraph(Graph &G) 
+//     {
+//       checkCompileExtendableGraph(G);
+//       checkCompileGraphEraseNode(G);
+//       checkCompileGraphEraseEdge(G);
+//     }
+
+//     ///Checks whether a graph has findEdge() member function.
+    
+//     ///\todo findEdge() might be a global function.
+//     ///
+//     template<class Graph> void checkCompileGraphFindEdge(Graph &G) 
+//     {
+//       typedef typename Graph::NodeIt Node;
+//       typedef typename Graph::NodeIt NodeIt;
+
+//       G.findEdge(NodeIt(G),++NodeIt(G),G.findEdge(NodeIt(G),++NodeIt(G)));
+//       G.findEdge(Node(),Node(),G.findEdge(Node(),Node()));  
+//     }
+
+
+
+    /************* New GraphBase stuff **************/
+
+
+    /// \bug The nodes and edges are not allowed to inherit from the
+    /// same baseclass.
+
+    class BaseGraphItem {
     public:
-      /// Defalult constructor.
+      BaseGraphItem() {}
+      BaseGraphItem(Invalid) {}
 
-      /// Defalult constructor.
-      ///
-      StaticGraph() { }
-      ///Copy consructor.
+      // We explicitely list these:
+      BaseGraphItem(BaseGraphItem const&) {}
+      BaseGraphItem& operator=(BaseGraphItem const&) { return *this; }
 
-//       ///\todo It is not clear, what we expect from a copy constructor.
-//       ///E.g. How to assign the nodes/edges to each other? What about maps?
-//       StaticGraph(const StaticGraph& g) { }
+      bool operator==(BaseGraphItem) const { return false; }
+      bool operator!=(BaseGraphItem) const { return false; }
 
-      /// The base type of node iterators, 
-      /// or in other words, the trivial node iterator.
-
-      /// This is the base type of each node iterator,
-      /// thus each kind of node iterator converts to this.
-      /// More precisely each kind of node iterator should be inherited 
-      /// from the trivial node iterator.
-      class Node {
-      public:
-	/// Default constructor
-
-	/// @warning The default constructor sets the iterator
-	/// to an undefined value.
-	Node() { }
-	/// Copy constructor.
-
-	/// Copy constructor.
-	///
-	Node(const Node&) { }
-
-	/// Invalid constructor \& conversion.
-
-	/// This constructor initializes the iterator to be invalid.
-	/// \sa Invalid for more details.
-	Node(Invalid) { }
-	/// Equality operator
-
-	/// Two iterators are equal if and only if they point to the
-	/// same object or both are invalid.
-	bool operator==(Node) const { return true; }
-
-	/// Inequality operator
-	
-	/// \sa operator==(Node n)
-	///
-	bool operator!=(Node) const { return true; }
-
- 	///Comparison operator.
-
-	///This is a strict ordering between the nodes.
-	///
-	///This ordering can be different from the order in which NodeIt
-	///goes through the nodes.
-	///\todo Possibly we don't need it.
-	bool operator<(Node) const { return true; }
-      };
-    
-      /// This iterator goes through each node.
-
-      /// This iterator goes through each node.
-      /// Its usage is quite simple, for example you can count the number
-      /// of nodes in graph \c g of type \c Graph like this:
-      /// \code
-      /// int count=0;
-      /// for (Graph::NodeIt n(g); n!=INVALID; ++n) ++count;
-      /// \endcode
-      class NodeIt : public Node {
-      public:
-	/// Default constructor
-
-	/// @warning The default constructor sets the iterator
-	/// to an undefined value.
-	NodeIt() { }
-	/// Copy constructor.
-	
-	/// Copy constructor.
-	///
-	NodeIt(const NodeIt&) { }
-	/// Invalid constructor \& conversion.
-
-	/// Initialize the iterator to be invalid.
-	/// \sa Invalid for more details.
-	NodeIt(Invalid) { }
-	/// Sets the iterator to the first node.
-
-	/// Sets the iterator to the first node of \c g.
-	///
-	NodeIt(const StaticGraph& g) { }
-	/// Node -> NodeIt conversion.
-
-	/// Sets the iterator to the node of \c g pointed by the trivial 
-	/// iterator n.
-	/// This feature necessitates that each time we 
-	/// iterate the edge-set, the iteration order is the same.
-	NodeIt(const StaticGraph& g, const Node& n) { }
-	/// Next node.
-
-	/// Assign the iterator to the next node.
-	///
-	NodeIt& operator++() { return *this; }
-      };
-    
-    
-      /// The base type of the edge iterators.
-
-      /// The base type of the edge iterators.
-      ///
-      class Edge {
-      public:
-	/// Default constructor
-
-	/// @warning The default constructor sets the iterator
-	/// to an undefined value.
-	Edge() { }
-	/// Copy constructor.
-
-	/// Copy constructor.
-	///
-	Edge(const Edge&) { }
-	/// Initialize the iterator to be invalid.
-
-	/// Initialize the iterator to be invalid.
-	///
-	Edge(Invalid) { }
-	/// Equality operator
-
-	/// Two iterators are equal if and only if they point to the
-	/// same object or both are invalid.
-	bool operator==(Edge) const { return true; }
-	/// Inequality operator
-
-	/// \sa operator==(Node n)
-	///
-	bool operator!=(Edge) const { return true; }
- 	///Comparison operator.
-
-	///This is a strict ordering between the nodes.
-	///
-	///This ordering can be different from the order in which NodeIt
-	///goes through the nodes.
-	///\todo Possibly we don't need it.
- 	bool operator<(Edge) const { return true; }
-      };
-    
-      /// This iterator goes trough the outgoing edges of a node.
-
-      /// This iterator goes trough the \e outgoing edges of a certain node
-      /// of a graph.
-      /// Its usage is quite simple, for example you can count the number
-      /// of outgoing edges of a node \c n
-      /// in graph \c g of type \c Graph as follows.
-      /// \code
-      /// int count=0;
-      /// for (Graph::OutEdgeIt e(g, n); e!=INVALID; ++e) ++count;
-      /// \endcode
-    
-      class OutEdgeIt : public Edge {
-      public:
-	/// Default constructor
-
-	/// @warning The default constructor sets the iterator
-	/// to an undefined value.
-	OutEdgeIt() { }
-	/// Copy constructor.
-
-	/// Copy constructor.
-	///
-	OutEdgeIt(const OutEdgeIt&) { }
-	/// Initialize the iterator to be invalid.
-
-	/// Initialize the iterator to be invalid.
-	///
-	OutEdgeIt(Invalid) { }
-	/// This constructor sets the iterator to first outgoing edge.
-    
-	/// This constructor set the iterator to the first outgoing edge of
-	/// node
-	///@param n the node
-	///@param g the graph
-	OutEdgeIt(const StaticGraph& g, const Node& n) { }
-	/// Edge -> OutEdgeIt conversion
-
-	/// Sets the iterator to the value of the trivial iterator \c e.
-	/// This feature necessitates that each time we 
-	/// iterate the edge-set, the iteration order is the same.
-	OutEdgeIt(const StaticGraph& g, const Edge& e) { }
-	///Next outgoing edge
-	
-	/// Assign the iterator to the next 
-	/// outgoing edge of the corresponding node.
-	OutEdgeIt& operator++() { return *this; }
-      };
-
-      /// This iterator goes trough the incoming edges of a node.
-
-      /// This iterator goes trough the \e incoming edges of a certain node
-      /// of a graph.
-      /// Its usage is quite simple, for example you can count the number
-      /// of outgoing edges of a node \c n
-      /// in graph \c g of type \c Graph as follows.
-      /// \code
-      /// int count=0;
-      /// for(Graph::InEdgeIt e(g, n); e!=INVALID; ++e) ++count;
-      /// \endcode
-
-      class InEdgeIt : public Edge {
-      public:
-	/// Default constructor
-
-	/// @warning The default constructor sets the iterator
-	/// to an undefined value.
-	InEdgeIt() { }
-	/// Copy constructor.
-
-	/// Copy constructor.
-	///
-	InEdgeIt(const InEdgeIt&) { }
-	/// Initialize the iterator to be invalid.
-
-	/// Initialize the iterator to be invalid.
-	///
-	InEdgeIt(Invalid) { }
-	/// This constructor sets the iterator to first incoming edge.
-    
-	/// This constructor set the iterator to the first incoming edge of
-	/// node
-	///@param n the node
-	///@param g the graph
-	InEdgeIt(const StaticGraph& g, const Node& n) { }
-	/// Edge -> InEdgeIt conversion
-
-	/// Sets the iterator to the value of the trivial iterator \c e.
-	/// This feature necessitates that each time we 
-	/// iterate the edge-set, the iteration order is the same.
-	InEdgeIt(const StaticGraph& g, const Edge& n) { }
-	/// Next incoming edge
-
-	/// Assign the iterator to the next inedge of the corresponding node.
-	///
-	InEdgeIt& operator++() { return *this; }
-      };
-      /// This iterator goes through each edge.
-
-      /// This iterator goes through each edge of a graph.
-      /// Its usage is quite simple, for example you can count the number
-      /// of edges in a graph \c g of type \c Graph as follows:
-      /// \code
-      /// int count=0;
-      /// for(Graph::EdgeIt e(g); e!=INVALID; ++e) ++count;
-      /// \endcode
-      class EdgeIt : public Edge {
-      public:
-	/// Default constructor
-
-	/// @warning The default constructor sets the iterator
-	/// to an undefined value.
-	EdgeIt() { }
-	/// Copy constructor.
-
-	/// Copy constructor.
-	///
-	EdgeIt(const EdgeIt&) { }
-	/// Initialize the iterator to be invalid.
-
-	/// Initialize the iterator to be invalid.
-	///
-	EdgeIt(Invalid) { }
-	/// This constructor sets the iterator to first edge.
-    
-	/// This constructor set the iterator to the first edge of
-	/// node
-	///@param g the graph
-	EdgeIt(const StaticGraph& g) { }
-	/// Edge -> EdgeIt conversion
-
-	/// Sets the iterator to the value of the trivial iterator \c e.
-	/// This feature necessitates that each time we 
-	/// iterate the edge-set, the iteration order is the same.
-	EdgeIt(const StaticGraph&, const Edge&) { } 
-    	///Next edge
-	
-	/// Assign the iterator to the next 
-	/// edge of the corresponding node.
-	EdgeIt& operator++() { return *this; }
-      };
-
-      /// First node of the graph.
-
-      /// \retval i the first node.
-      /// \return the first node.
-      ///
-      NodeIt& first(NodeIt& i) const { return i; }
-
-      /// The first incoming edge.
-
-      /// The first incoming edge.
-      ///
-      InEdgeIt& first(InEdgeIt &i, Node) const { return i; }
-      /// The first outgoing edge.
-
-      /// The first outgoing edge.
-      ///
-      OutEdgeIt& first(OutEdgeIt& i, Node) const { return i; }
-      /// The first edge of the Graph.
-
-      /// The first edge of the Graph.
-      ///
-      EdgeIt& first(EdgeIt& i) const { return i; }
-
-      ///Gives back the head node of an edge.
-
-      ///Gives back the head node of an edge.
-      ///
-      Node head(Edge) const { return INVALID; }
-      ///Gives back the tail node of an edge.
-
-      ///Gives back the tail node of an edge.
-      ///
-      Node tail(Edge) const { return INVALID; }
-  
-      ///Gives back the \e id of a node.
-
-      ///\warning Not all graph structures provide this feature.
-      ///
-      ///\todo Should each graph provide \c id?
-      int id(const Node&) const { return 0; }
-      ///Gives back the \e id of an edge.
-
-      ///\warning Not all graph structures provide this feature.
-      ///
-      ///\todo Should each graph provide \c id?
-      int id(const Edge&) const { return 0; }
-
-      ///\e
-      
-      ///\todo Should it be in the concept?
-      ///
-      int nodeNum() const { return 0; }
-      ///\e
-
-      ///\todo Should it be in the concept?
-      ///
-      int edgeNum() const { return 0; }
-
-
-      ///Reference map of the nodes to type \c T.
-
-      /// \ingroup skeletons
-      ///Reference map of the nodes to type \c T.
-      /// \sa Reference
-      /// \warning Making maps that can handle bool type (NodeMap<bool>)
-      /// needs some extra attention!
-      template<class T> class NodeMap : public ReferenceMap< Node, T >
-      {
-      public:
-
-	///\e
-	NodeMap(const StaticGraph&) { }
-	///\e
-	NodeMap(const StaticGraph&, T) { }
-
-	///Copy constructor
-	template<typename TT> NodeMap(const NodeMap<TT>&) { }
-	///Assignment operator
-	template<typename TT> NodeMap& operator=(const NodeMap<TT>&)
-	{ return *this; }
-      };
-
-      ///Reference map of the edges to type \c T.
-
-      /// \ingroup skeletons
-      ///Reference map of the edges to type \c T.
-      /// \sa Reference
-      /// \warning Making maps that can handle bool type (EdgeMap<bool>)
-      /// needs some extra attention!
-      template<class T> class EdgeMap
-	: public ReferenceMap<Edge,T>
-      {
-      public:
-
-	///\e
-	EdgeMap(const StaticGraph&) { }
-	///\e
-	EdgeMap(const StaticGraph&, T) { }
-    
-	///Copy constructor
-	template<typename TT> EdgeMap(const EdgeMap<TT>&) { }
-	///Assignment operator
-	template<typename TT> EdgeMap &operator=(const EdgeMap<TT>&)
-	{ return *this; }
-      };
+      // Technical requirement. Do we really need this?
+      bool operator<(BaseGraphItem) const { return false; }
     };
 
-    struct DummyType {
-      int value;
-      DummyType() {}
-      DummyType(int p) : value(p) {}
-      DummyType& operator=(int p) { value = p; return *this;}
+
+    /// A minimal GraphBase concept
+
+    /// This class describes a minimal concept which can be extended to a
+    /// full-featured graph with \ref GraphFactory.
+    class GraphBase {
+    public:
+
+      GraphBase() {}
+
+
+      /// \bug Nodes and Edges are comparable each other
+      
+      class Node : public BaseGraphItem {};
+      class Edge : public BaseGraphItem {};
+
+      // Graph operation
+      void firstNode(Node &n) const { }
+      void firstEdge(Edge &e) const { }
+
+      void firstOutEdge(Edge &e, Node) const { }
+      void firstInEdge(Edge &e, Node) const { }
+
+      void nextNode(Node &n) const { }
+      void nextEdge(Edge &e) const { }
+
+
+      // Question: isn't it reasonable if this methods have a Node
+      // parameter? Like this:
+      // Edge& nextOut(Edge &e, Node) const { return e; }
+      void nextOutEdge(Edge &e) const { }
+      void nextInEdge(Edge &e) const { }
+
+      Node head(Edge) const { return Node(); }
+      Node tail(Edge) const { return Node(); }
+      
+
+      // Do we need id, nodeNum, edgeNum and co. in this basic graphbase
+      // concept?
+
+
+      // Maps.
+      //
+      // We need a special slimer concept which does not provide maps (it
+      // wouldn't be strictly slimer, cause for map-factory id() & friends
+      // a required...)
+
+      template<typename T>
+      class NodeMap : public GraphMap<Node, T, GraphBase> {};
+
+      template<typename T>
+      class EdgeMap : public GraphMap<Edge, T, GraphBase> {};
     };
-    
-    ///\brief Checks whether \c G meets the
-    ///\ref lemon::skeleton::StaticGraph "StaticGraph" concept
-    template<class Graph> void checkCompileStaticGraph(Graph &G) 
-    {
-      typedef typename Graph::Node Node;
-      typedef typename Graph::NodeIt NodeIt;
-      typedef typename Graph::Edge Edge;
-      typedef typename Graph::EdgeIt EdgeIt;
-      typedef typename Graph::InEdgeIt InEdgeIt;
-      typedef typename Graph::OutEdgeIt OutEdgeIt;
-  
-      {
-	Node i; Node j(i); Node k(INVALID);
-	i=j;
-	bool b; b=true;
-	b=(i==INVALID); b=(i!=INVALID);
-	b=(i==j); b=(i!=j); b=(i<j);
-      }
-      {
-	NodeIt i; NodeIt j(i); NodeIt k(INVALID); NodeIt l(G);
-	i=j;
-	j=G.first(i);
-	j=++i;
-	bool b; b=true;
-	b=(i==INVALID); b=(i!=INVALID);
-	Node n(i);
-	n=i;
-	b=(i==j); b=(i!=j); b=(i<j);
-	//Node ->NodeIt conversion
-	NodeIt ni(G,n);
-      }
-      {
-	Edge i; Edge j(i); Edge k(INVALID);
-	i=j;
-	bool b; b=true;
-	b=(i==INVALID); b=(i!=INVALID);
-	b=(i==j); b=(i!=j); b=(i<j);
-      }
-      {
-	EdgeIt i; EdgeIt j(i); EdgeIt k(INVALID); EdgeIt l(G);
-	i=j;
-	j=G.first(i);
-	j=++i;
-	bool b; b=true;
-	b=(i==INVALID); b=(i!=INVALID);
-	Edge e(i);
-	e=i;
-	b=(i==j); b=(i!=j); b=(i<j);
-	//Edge ->EdgeIt conversion
-	EdgeIt ei(G,e);
-      }
-      {
-	Node n;
-	InEdgeIt i; InEdgeIt j(i); InEdgeIt k(INVALID); InEdgeIt l(G,n);
-	i=j;
-	j=G.first(i,n);
-	j=++i;
-	bool b; b=true;
-	b=(i==INVALID); b=(i!=INVALID);
-	Edge e(i);
-	e=i;
-	b=(i==j); b=(i!=j); b=(i<j);
-	//Edge ->InEdgeIt conversion
-	InEdgeIt ei(G,e);
-      }
-      {
-	Node n;
-	OutEdgeIt i; OutEdgeIt j(i); OutEdgeIt k(INVALID); OutEdgeIt l(G,n);
-	i=j;
-	j=G.first(i,n);
-	j=++i;
-	bool b; b=true;
-	b=(i==INVALID); b=(i!=INVALID);
-	Edge e(i);
-	e=i;
-	b=(i==j); b=(i!=j); b=(i<j);
-	//Edge ->OutEdgeIt conversion
-	OutEdgeIt ei(G,e);
-      }
-      {
-	Node n,m;
-	n=m=INVALID;
-	Edge e;
-	e=INVALID;
-	n=G.tail(e);
-	n=G.head(e);
-      }
-      // id tests
-      { Node n; int i=G.id(n); i=i; }
-      { Edge e; int i=G.id(e); i=i; }
-      //NodeMap tests
-      {
-	Node k;
-	typename Graph::template NodeMap<int> m(G);
-	//Const map
-	typename Graph::template NodeMap<int> const &cm = m;
-	//Inicialize with default value
-	typename Graph::template NodeMap<int> mdef(G,12);
-	//Copy
-	typename Graph::template NodeMap<int> mm(cm);
-	//Copy from another type
-	typename Graph::template NodeMap<double> dm(cm);
-	//Copy to more complex type
-	typename Graph::template NodeMap<DummyType> em(cm);
-	int v;
-	v=m[k]; m[k]=v; m.set(k,v);
-	v=cm[k];
-    
-	m=cm;  
-	dm=cm; //Copy from another type  
-	em=cm; //Copy to more complex type
-	{
-	  //Check the typedef's
-	  typename Graph::template NodeMap<int>::ValueType val;
-	  val=1;
-	  typename Graph::template NodeMap<int>::KeyType key;
-	  key = typename Graph::NodeIt(G);
-	}
-      }  
-      { //bool NodeMap
-	Node k;
-	typename Graph::template NodeMap<bool> m(G);
-	typename Graph::template NodeMap<bool> const &cm = m;  //Const map
-	//Inicialize with default value
-	typename Graph::template NodeMap<bool> mdef(G,12);
-	typename Graph::template NodeMap<bool> mm(cm);   //Copy
-	typename Graph::template NodeMap<int> dm(cm); //Copy from another type
-	bool v;
-	v=m[k]; m[k]=v; m.set(k,v);
-	v=cm[k];
-    
-	m=cm;  
-	dm=cm; //Copy from another type
-	m=dm; //Copy to another type
 
-	{
-	  //Check the typedef's
-	  typename Graph::template NodeMap<bool>::ValueType val;
-	  val=true;
-	  typename Graph::template NodeMap<bool>::KeyType key;
-	  key= typename Graph::NodeIt(G);
+
+
+    /**************** Concept checking classes ****************/
+
+    template<typename BGI>
+    struct BaseGraphItemConcept {
+      void constraints() {
+	BGI i1;
+	BGI i2 = i1;
+	BGI i3 = INVALID;
+	
+	i1 = i3;
+	if( i1 == i3 ) {
+	  if ( i2 != i3 && i3 < i2 )
+	    return;
 	}
       }
-      //EdgeMap tests
-      {
-	Edge k;
-	typename Graph::template EdgeMap<int> m(G);
-	typename Graph::template EdgeMap<int> const &cm = m;  //Const map
-	//Inicialize with default value
-	typename Graph::template EdgeMap<int> mdef(G,12);
-	typename Graph::template EdgeMap<int> mm(cm);   //Copy
-	typename Graph::template EdgeMap<double> dm(cm);//Copy from another type
-	int v;
-	v=m[k]; m[k]=v; m.set(k,v);
-	v=cm[k];
-    
-	m=cm;  
-	dm=cm; //Copy from another type
-	{
-	  //Check the typedef's
-	  typename Graph::template EdgeMap<int>::ValueType val;
-	  val=1;
-	  typename Graph::template EdgeMap<int>::KeyType key;
-	  key= typename Graph::EdgeIt(G);
-	}
-      }  
-      { //bool EdgeMap
-	Edge k;
-	typename Graph::template EdgeMap<bool> m(G);
-	typename Graph::template EdgeMap<bool> const &cm = m;  //Const map
-	//Inicialize with default value
-	typename Graph::template EdgeMap<bool> mdef(G,12);
-	typename Graph::template EdgeMap<bool> mm(cm);   //Copy
-	typename Graph::template EdgeMap<int> dm(cm); //Copy from another type
-	bool v;
-	v=m[k]; m[k]=v; m.set(k,v);
-	v=cm[k];
-    
-	m=cm;  
-	dm=cm; //Copy from another type
-	m=dm; //Copy to another type
-	{
-	  //Check the typedef's
-	  typename Graph::template EdgeMap<bool>::ValueType val;
-	  val=true;
-	  typename Graph::template EdgeMap<bool>::KeyType key;
-	  key= typename Graph::EdgeIt(G);
-	}
-      }
-    }
-    
-    /// An empty non-static graph class.
-    
-    /// This class provides everything that \ref StaticGraph
-    /// with additional functionality which enables to build a
-    /// graph from scratch.
-    class ExtendableGraph : public StaticGraph
-    {
-    public:
-      /// Defalult constructor.
-
-      /// Defalult constructor.
-      ///
-      ExtendableGraph() { }
-      ///Add a new node to the graph.
-
-      /// \return the new node.
-      ///
-      Node addNode() { return INVALID; }
-      ///Add a new edge to the graph.
-
-      ///Add a new edge to the graph with tail node \c t
-      ///and head node \c h.
-      ///\return the new edge.
-      Edge addEdge(Node h, Node t) { return INVALID; }
-    
-      /// Resets the graph.
-
-      /// This function deletes all edges and nodes of the graph.
-      /// It also frees the memory allocated to store them.
-      /// \todo It might belong to \ref ErasableGraph.
-      void clear() { }
     };
 
     
-    ///\brief Checks whether \c G meets the
-    ///\ref lemon::skeleton::ExtendableGraph "ExtendableGraph" concept
-    template<class Graph> void checkCompileExtendableGraph(Graph &G) 
-    {
-      checkCompileStaticGraph(G);
+    
+    class StaticGraph 
+      :  virtual public BaseGraphComponent, public IterableGraphComponent, public MappableGraphComponent {
+    public:
+      typedef BaseGraphComponent::Node Node;
+      typedef BaseGraphComponent::Edge Edge;
+    };
 
-      typedef typename Graph::Node Node;
-      typedef typename Graph::NodeIt NodeIt;
-      typedef typename Graph::Edge Edge;
-      typedef typename Graph::EdgeIt EdgeIt;
-      typedef typename Graph::InEdgeIt InEdgeIt;
-      typedef typename Graph::OutEdgeIt OutEdgeIt;
-  
-      Node n,m;
-      n=G.addNode();
-      m=G.addNode();
-      Edge e;
-      e=G.addEdge(n,m); 
-  
-      //  G.clear();
-    }
+    template <typename Graph>
+    struct StaticGraphConcept {
+      void constraints() {
+	function_requires<BaseGraphComponentConcept<Graph> >();
+	function_requires<IterableGraphComponentConcept<Graph> >();
+	function_requires<MappableGraphComponentConcept<Graph> >();
+      }
+      Graph& graph;
+    };
 
+    class ExtendableGraph 
+      :  virtual public BaseGraphComponent, public StaticGraph, public ExtendableGraphComponent, public ClearableGraphComponent {
+    public:
+      typedef BaseGraphComponent::Node Node;
+      typedef BaseGraphComponent::Edge Edge;
+    };
 
-    /// An empty erasable graph class.
-  
-    /// This class is an extension of \ref ExtendableGraph. It also makes it
-    /// possible to erase edges or nodes.
-    class ErasableGraph : public ExtendableGraph
-    {
+    template <typename Graph>
+    struct ExtendableGraphConcept {
+      void constraints() {
+	function_requires<StaticGraphConcept<Graph> >();
+	function_requires<ExtendableGraphComponentConcept<Graph> >();
+	function_requires<ClearableGraphComponentConcept<Graph> >();
+      }
+      Graph& graph;
+    };
+
+    class ErasableGraph 
+      :  virtual public BaseGraphComponent, public ExtendableGraph, public ErasableGraphComponent {
     public:
-      /// Defalult constructor.
+      typedef BaseGraphComponent::Node Node;
+      typedef BaseGraphComponent::Edge Edge;
+    };
 
-      /// Defalult constructor.
-      ///
-      ErasableGraph() { }
-      /// Deletes a node.
+    template <typename Graph>
+    struct ErasableGraphConcept {
+      void constraints() {
+	function_requires<ExtendableGraphConcept<Graph> >();
+	function_requires<ErasableGraphComponentConcept<Graph> >();
+      }
+      Graph& graph;
+    };
 
-      /// Deletes node \c n node.
-      ///
-      void erase(Node n) { }
-      /// Deletes an edge.
-
-      /// Deletes edge \c e edge.
-      ///
-      void erase(Edge e) { }
-    };
-    
-    template<class Graph> void checkCompileGraphEraseEdge(Graph &G) 
-    {
-      typename Graph::Edge e;
-      G.erase(e);
-    }
-
-    template<class Graph> void checkCompileGraphEraseNode(Graph &G) 
-    {
-      typename Graph::Node n;
-      G.erase(n);
-    }
-
-    ///\brief Checks whether \c G meets the
-    ///\ref lemon::skeleton::EresableGraph "EresableGraph" concept
-    template<class Graph> void checkCompileErasableGraph(Graph &G) 
-    {
-      checkCompileExtendableGraph(G);
-      checkCompileGraphEraseNode(G);
-      checkCompileGraphEraseEdge(G);
-    }
-
-    ///Checks whether a graph has findEdge() member function.
-    
-    ///\todo findEdge() might be a global function.
-    ///
-    template<class Graph> void checkCompileGraphFindEdge(Graph &G) 
-    {
-      typedef typename Graph::NodeIt Node;
-      typedef typename Graph::NodeIt NodeIt;
-
-      G.findEdge(NodeIt(G),++NodeIt(G),G.findEdge(NodeIt(G),++NodeIt(G)));
-      G.findEdge(Node(),Node(),G.findEdge(Node(),Node()));  
-    }
- 
     // @}
   } //namespace skeleton  
 } //namespace lemon