CLASS & TYPE

• IN MOST SYSTEMS TYPE & CLASS ARE USED INTERCHANGEABLY
• IF BOTH ARE PRESENT THEN:
  
  
  • TYPE: SPECIFICATION OF THE INTERFACE OF A SET OF OBJECTS
  • CLASS: IS AN IMPLEMENTATION NOTION
  
  
• CLASS DEFINES THE IMPLEMENTATION OF - WHILE TYPE DESCRIBES HOW OBJECTS CAN BE USED
  
  
  • A TYPE CAN BE IMPLEMENTED BY SEVERAL CLASSES (ALTERNATE IMPLEMENTATIONS)
  • A CLASS CAN IMPLEMENT SEVERAL TYPES (DIFFERENT OBJECT BEHAVIORS)
  • TYPE: FUNCTIONAL SPEC; CLASS: SET OF "VIRTUAL MACHINES" SATISFYING ONE OR MORE FUNCTIONAL SPECS
  
  

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Ugo O. Gagliardi
GSD-6306 Spring 2003-2004