Object Oriented Programming (first version -- of three) 

	Programming methodology in which the data elements (objects) in 
	the system form the fundamental unit of program decomposition.  



	Object Oriented Programming  (second version)

	Programming methodology in which the data elements (objects) in 
	the system form the fundamental unit of program decomposition.  
	Objects are described by means of classes.  




	Object Principle


	Objects are autonomous actors.  They respond to messages by 
	executing methods.  The execution of a method may require 
	sending additional messages   




	Class Principle


	Classes are both collections and descriptions of objects.  
	A class provides a template, or factory, for creation of objects 
	of the same kind.  




	Inheritance



	Using one class to define another by declaring only the new features.  
	Defines a subclass relationship between the original (parent) class 
	and the new class. All objects in the new class are members of the old 
	class. 




	Type Specialization Principle

	In any context in which an object of a given class may be used, any 
	object of a subclass may be substituted.



	Object Oriented Programming  (final version)

	Programming methodology in which the data elements (objects) in the 
	system form the fundamental unit of program decomposition.  Objects 
	are described by means of classes.  Classes are developed by means of 
	successive refinement using inheritance.




	Principle of Abstraction

  	The processing provided by a class should always be in accord with the
	nature of the abstraction on which the class is based. 



       
       Class Invariant



	A statement guaranteed by the implementor to be always true when 
	observed from outside the class. 




	Information Hiding Principle

	Details of the implementation of a data type should not be accessible 
	to clients of that data type.  



	Type Polymorphism

	The ability of a name to refer to objects of many different types.  



	ISA

	A relationship between a subclass and its superclass.  Other 
	relationships are possible but this is the norm.  An object of a 
	subclass ISA (is a) object of its superclass.  It exhibits all 
	of the properties of a superclass object.  Implies that the 
	subclass is a specialization of the superclass.  



	ISLike

	A relationship between a class and its superclass.  A weaker 
	relationship than ISA.  It is used only for code reuse rather than 
	as an abstraction mechanism.  Implies that the subclass is a 
	modification of its uperclass.  Some item of the semantics has changed.  



	HASA (uses)

	A relationship between classes.  The relationship A HASA B is true 
	if B is used to implement A.  One of A's components is an element 
	in B.  Sometimes we make a choice   between ISA and HASA 
	when designing a new class.  



   
   
	Dynamic Binding Principle


	Every virtual message that is sent is interpreted in the context of the 
	object executing the method.