Layered structure

The term ``Layered structure'' is often used as a synonym for ``tree structure.'' However, the layered structures in natural systems are not so simple as tree structures. Some of them are more similar to DAG structures (directed acyclic graph structures). If the system is continuous, even DAG is not sufficient for the model of the system.

Y. Kanada (yasusi @
Created: 11/21/95, Modified: 5/6/2002.