Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!apple!well!al
From: al@well.sf.ca.us (Alfred Fontes)
Newsgroups: comp.object
Subject: Visibility in Booch's book
Message-ID: <21243@well.sf.ca.us>
Date: 19 Oct 90 00:53:16 GMT
Distribution: comp
Lines: 14


In his book "Object Oriented Design with Applications", Grady Booch 
says: 
   If we decide that object X sends message M to object Y, then either 
   directly or indirectly, X's class must be visible to Y's class, 
   otherwise, we could not name the operation M in the body of X's 
   class... (p. 127)
It seems to me that the reverse is true: Y should be visible to X.  X 
is sending the message to Y, and must therefore be aware of Y's 
interface.  But why should Y need to know where message M is coming 
from, as long as the message is valid?  

I would really appreciate someone clearing this up for me, because this 
point occurs several times in the chapter.