Classes that perform long tasks (like graph algorithms) can implement this interface
so that they can be monitored by a GUI like a javax.swing.plaf.ProgressBarUI or a
javax.swing.ProgressMonitor
Nodes and Edges comprise an additional directed graph through the
contains-a relationship, in which a MetaParent Node contains each of its
MetaChild Nodes and Edges.
Nodes and Edges comprise an additional directed graph through the
contains-a relationship, in which a MetaParent Node contains each of its
MetaChild Nodes and Edges.