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From: rmartin@rcmcon.com (Robert Martin)
Subject: Re: Teaching OO
References: <D2150022.kfebd9@ed.bse.com>
Organization: R. C. M. Consulting Inc. 708-918-1004
Date: Mon, 23 Jan 1995 18:18:23 GMT
Message-ID: <1995Jan23.181823.12490@rcmcon.com>
Lines: 42
Xref: glinda.oz.cs.cmu.edu comp.object:25512 comp.lang.smalltalk:19819

rmartin said, regarding applications that are difficult to model with OOD:
>> The reason is simple.  In such domains the data exists before the
>> applications.  There are an undefined number of applications that can
>> operate upon the data.  Some will be specified up front, but many
>> others will need to be written over time.  There will be no end to
>> these applications.  As long as the data exists, new ways of
>> manipulating it will be needed.  

>The object-oriented information warehouse application that I worked
>on is able to handle these situations. Of course, it treats data in
>much the same manner as a parameter-driven computer-integrated-manufacturing
>application treats changes in the manufacturing process. Further, as
>you point out, the application did not directly model the data structure.

>> Thus, it will be impossible to include the methods that operate upon
>> the data in an object model of the data.  In one sense, the object
>> model can never be completed.  One could continue to open the objects
>> and add methods, however this leads to unlimited code bloat within the
>> objects.  Nobody wants to link the code for every application into
>> their particular application.  So the code will have to be exported
>> out of the objects and into the applications.

>I agree with you. Unfortunately, I see and hear about people
>every day who attempt to build "OO" applications by modelling
>the objects based on the _structure_ of the data.

Many people think that if the objects model the structure of the data,
then they are "modeling the real world".  This is why I react to this
catchphrase when I hear it (or read it).  Anyway, it would appear that
we are in agreement.







-- 
Robert Martin       | Design Consulting   | Training courses offered:
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