The Generic Tree Editor
-----------------------
Trees that are made by a tree editor are a special kind of graph 
consisting of nodes and edges and with a certain representation. 
 
This tool is intended for generic trees in which all nodes are text 
labels. 

Trees should satisfy certain constraints. Most constraints
are specific for the particular technique supported by the editor. 
The most important constraints on trees are that they have a single 
root node and that they do not contain cycles,

Tree editors have two modes: Editable graph and View as Tree
mode which can be set with a pair of radio buttons on the left side of
the main window. In the first mode trees are edited just like in any
diagram editor whereas in the other mode trees are drawn in a special
layout and they cannot be edited.
 
More about tree editors can be found in chapter 8 of the user's guide.
