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From: nospam@somewhere.ia.us (Robert S. White)
Subject: Re: Interface/Implementation (was Re: Design by Contract)
Date: 1997/09/11
Message-ID: <5v7mhr$meo$2@flood.weeg.uiowa.edu>#1/1
X-Deja-AN: 271483042
References: <EG0nDv.EJD@ecf.toronto.edu> <EG7zJn.366@syd.csa.com.au>
 <EG9wrJ.F3t@ecf.toronto.edu>
Organization: designing/implementing avionics during the day
Newsgroups: comp.object,comp.software-eng,comp.lang.ada,comp.lang.eiffel
Date: 1997-09-11T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <EG9wrJ.F3t@ecf.toronto.edu>, doylep@ecf.toronto.edu says...
>
>In article <EG7zJn.366@syd.csa.com.au>,
>Don Harrison <nospam@thanks.com.au> wrote:
>>
>>By comparison, the purpose of deferred classes is to specify what 
>>functionality will be provided by descendants of a class. 
>
>...which includes visibility information.  (Just for the record.  :-)
>
>>That is, it documents the inheritance
>>relation. This purpose is orthogonal to that of visibility. 
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>I think this seems to be using a pretty loose definition of "orthogonal".

   Don seems to be using the word orthogonal in a common usage i.e "right 
angles" per the root of the Greek word "orthos" (straight, regular, upright, 
correct, standard).

>Inheritance can be inheritance of interface and/or inheritance of
>implementation.  Interface inheritance means inheriting visibility
>information.
>
>Orthogonal means that anything achieved using one technique cannot
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>be achieved using the other.  But specifying implementation (ie.
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>the client relationship) can be accomplished by inheritance, so I'm
>not clear on how these are orthogonal.  (Perhaps I'm mistaken about
>what "orthogonal" means?  I'm going on recollections of a book I
>read a while back.)

  I just now went back to Webster's New Universal Unabridged (not quite
the OED?) but fairly long for its 2000+ pages.  Seems to me that your
definition of orthogonal is a bit restrictive.  In the context of 
Don's use it seems the word orthogonal is being used to say that the 
reason behind the functionality purpose is at "right angles" to that 
of the visibility purpose.
_____________________________________________________________________
Robert S. White         -- An embedded systems software engineer
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