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general hierarchy
subject			fact

general hierarchy	has definition A pattern in which two classes are related both by a generalization and by a one to many association, such that the generated graph of instances forms a hierarchy
	has antipatterns modelling a hierarchy of categories using a hierarchy of classes
	has context many class diagrams where you often find a set of objects that have a naturally hierarchical relationship.
	has forces You want a flexible way of representing the hierarchy that naturally prevents certain objects from having subordinates You also have to account for the fact that all the objects share common properties and operations
	has problem How do you draw a class diagram to represent a hierarchy of objects, in which some objects cannot have subordinates?
	has related patterns the Reflexive Association pattern, the Composite pattern (a specialization of the General Hierarchy pattern)
	has solution Create an abstract «Node» class to represent the features possessed by each object in the hierarchy. Then create at least two subclasses of the «Node» class. One of the subclasses, «SuperiorNode», must be linked by a «subordinates» association to the superclass; whereas at least one subclass, «NonSuperiorNode», must not be. The subordinates of a «SuperiorNode» can thus be instances of either «SuperiorNode» or «NonSuperiorNode».
	is a subtopic of 6.3 - The General Hierarchy Pattern
	is an instance of design pattern
design pattern	has name
	has references one or more references which indicate who developed or inspired a pattern
	should be illustrated using a simple diagram
	should be written using a narrative writing style
pattern	should be as general as possible
	should be described in an easy-to-understand form so that people can determine when and how to use it
	should contain a solution that has been proven to effectively solve the problem in the indicated context

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