diff -r 677ea6c8169a -r 4cd528a30ec1 doc/graphs.dox
--- a/doc/graphs.dox	Wed Jun 28 16:27:44 2006 +0000
+++ b/doc/graphs.dox	Fri Jun 30 12:14:36 2006 +0000
@@ -9,20 +9,20 @@
 The primary data structures of LEMON are the graph classes. They all
 provide a node list - edge list interface, i.e. they have
 functionalities to list the nodes and the edges of the graph as well
-as  incoming and outgoing edges of a given node. 
+as  incoming and outgoing edges of a given node. This functionalities
+are defined in the \ref lemon::concept::Graph "Graph" concept.
 
-Each graph should meet the \ref lemon::concept::Graph "Graph" concept.
-This concept does not make it possible to change the graph (i.e. it is
-not possible to add or delete edges or nodes). Most of the graph
-algorithms will run on these graphs.
+The next important graph type concept is the undirected graph concept
+what is defined in the \ref lemon::concept::UGraph "UGraph" concept class.
+Each undirected graphs provide node - undirected edge list interfaces.
+In addition the undirected graphs can be used as directed graphs so
+they are also conform to the \ref lemon::concept::Graph "Graph" concept.
 
+Usually the graphs can be sorted to two group, the first is the
+general topology graph types which can store any graph and the second
+are the special topology graphs like the \ref FullUGraph or the \ref
+GridUGraph.
 
-In case of graphs meeting the full feature
-\ref lemon::concept::ErasableGraph "ErasableGraph"
-concept
-you can also erase individual edges and nodes in arbitrary order.
-
-The implemented graph structures are the following.
 \li \ref lemon::ListGraph "ListGraph" is the most versatile graph class. It meets
 the \ref lemon::concept::ErasableGraph "ErasableGraph" concept
 and it also has some convenient extra features.