Re: Class redefinition and class-changed.

[Danny Bobrow <Bobrow.pa@Xerox.COM>]

         The necessary and sufficient condition for this is to
         be able to get hold of an obsolete version of a class.  

    I don't agree.  We said in chapter 1 that the updating of the
    instances is done at an implementation-dependent time.  

I agree that your arguments imply your conclusion.  I think however,
that it would be better to say that "updating of the
instances is done at an implementation-dependent time sometime after the
class is redefined."   Since this is really an environment support
feature, I think we should specify that it will not occur before the
first method on an obsolete instance is called.  
  danny