INSTANTIATION MECHANISMS

• CLASS CAN BE SEEN AS A TEMPLATE OBJECT WHICH SPECIFIES:
  
  
  • STRUCTURE: SET OF INSTANCE'S ATTRIBUTES
  • SET OF OPERATIONS
  • SET OF METHODS: OPERATIONS IMPLEMENTATIONS
  
  
• CLASS-OBJECT: CONTAINS THE INFORMATION COMMON TO THE CLASS' INSTANCES - IN PARTICULAR THE METHODS

• PROTOTYPE OBJECT: CREATE NEW OBJECT BY MODIFYING AN EXISTING OBJECT'S ATTRIBUTE VALUES OR ITS BEHAVIOR
  
  
  • INSTANTIATION APPROACH SUPERIOR WHEN CLASS DEFINITIONS ARE STABLE
  • PROTOTYPE APPROACH SUPERIOR WHEN CLASS DEFINITIONS ARE EVOLVING
  
  
• AN OBJECT IS AN INSTANCE OF A CLASS C - BUT IS A MEMBER OF C's SUPERCLASSES
  
  
  • C IS THE MOST SPECIALIZED CLASS - ASSOCIATED WITH THE OBJECT - IN THE INHERITANCE HIERARCHY
  • MOST OO DATA MODELS RESTRICT AN OBJECT TO BE AN INSTANCE OF A SINGLE CLASS
  
  

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Ugo O. Gagliardi
GSD-6306 Spring 2003-2004