e object's position to its original position.</P>
<P>
<A NAME="IX_VisClass:tree management">
 </A>
Visible objects are maintained and managed in a tree structure. The tree has three basic elements: The root (topmost) node must be an object of <CODE>
VisContentClass</CODE>
. Any nodes in the middle of the tree, nodes that are allowed to have children, must be of <CODE>
VisCompClass</CODE>
. Any leaf nodes (guaranteed not to have children) may be of either <CODE>
VisClass</CODE>
 or <CODE>
VisCompClass</CODE>