The organization of class hierarchis identification of common attributes and functions among a group of related classes, and then combining them to form a new class. The new class then serves as the super class and the other work as subordinate classes. The new class may or may not have the meaning of an object by itself. If the object is created purely to combine the common attribute then it is called abstract class.
The process is repeated at different levels of abstraction with the sole objective of extending the classes. As hierarchy structure becomes progressively higher, the amount of specification and implementation inherited by the lower level of classes increases. The process is repeated untill we are sure that no new classes can be formed. For example see the two level interaction process.
The class hierarchy view displays the asserted and inferred class hierarchies. The asserted class hierarchy is visible by default.
The asserted class hierarchy view is one of the primary navigation devices in Protégé. It is presented as a tree where nodes in the tree represent classes. A child-parent relationship in the tree represents a sub/super class relationship in the class hierarchy.