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From: Richard Riehle <rriehle@nunic.nu.edu>
Subject: Re: Real OO
Date: 1996/05/09
Message-ID: <Pine.GSO.3.92.960509171645.1191B-100000@nunic.nu.edu>#1/1
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references: <slrn4p1bep.2dl.schlegel@pella.informatik.uni-rostock.de>
 <Dr4538.D27@assip.csasyd.oz>
to: Don Harrison <donh@syd.csa.com.au>
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organization: National University, San Diego
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Date: 1996-05-09T00:00:00+00:00
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On Thu, 9 May 1996, Don Harrison wrote:

> Juergen Schlegelmilch writes:
>
> :Yes, dispatch failure for multiple dispatch indicates broken polymorphism.
> :The design of inheritance hierarchies is often not seen in the light of
> :the Liskov Substitution Principle,
>      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Could you (or somone) explain what this is? Sorry, I'm a bit ignorant.


  You might want to look at a paper by Liskov, "Subtype Hierarchy and
  Implementation Hierarchy," Proceedings of the ACM Conference on
  Object-Oriented Programming, 1987


  Though the substitutability principle is often attributed to Liskov,
  it is also given treatment in a paper from Wegner and Zdonic,
  "Inheritance as an Incremental Modification Mechanism" published in
  the Proceedings of the European Conference on
  Object-Oriented Programming, 1988.

  An important overview of this subject is Cardelli and Wegner, "On
  Understanding Types, Data Abstraction, and Polymorphism," ACM
  Computing Surveys, Number 17, 1985.


  -- =================================================================

  All that academic stuff aside, the substitutability rule is quite
  useful when trying to determine whether one is organizing a set of
  objects by classification or by some other mechanism.  In particular,
  there is a point-of-view which says one should always apply the
  substitutability principle when attempting multiple inheritance.

  Richard Riehle