Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!cernvax!chx400!ugun2b!cui!oscar
From: oscar@cui.unige.ch (Oscar Nierstrasz)
Newsgroups: comp.software-eng
Subject: Re: Reusability considered harmful??(!!)
Keywords: Reusability, Division of Labor
Message-ID: <4842@cui.unige.ch>
Date: 31 Jan 91 09:30:43 GMT
References: <6108@stpstn.UUCP>
Organization: University of Geneva, Switzerland
Lines: 51

cox@stpstn.UUCP (Brad Cox) writes:

>Could it be that we (reusability proponents) are shooting ourself in
>the foot with the word, "reusability", just as the AI community did
>themselves in with a term of their own choosing, "artificial
>intelligence"?

There is another problem, which is that "reusability" is only part
(albeit an important one) of the story.  That is why I feel that it
is better to emphasize "software components" and even "component-oriented
software construction".  Even if you don't reuse a thing, it is important
to organize applications in terms of interlocking components as this
enhances robustness, maintainability and portability (though one could
argue that these are all instances of "micro-reusability").

The emphasis on "software components" also addresses the gap between
"object-oriented" programming (i.e., at the "chip" level) and software
construction without programming (as we know it).  A component can be
anything from a humble int to a customizable office system.  Furthermore,
the emphasis on "software construction" gets us away from the idea that
we must always be "programming" to build applications (another thing wrong
with the term "object-oriented programming").

Finally, there is another danger in the word "reusability", which simply
has to do with the fact that reusability does not come for free.  Anybody
who hears about a technology that supports reusability will naturally say,
"Yes, that's for me!  I would sure like to reuse software rather than
build it from scratch!"  Except the other half of the story is that someone
must build the reusable components.  Unfortunately this half of the
story is not well understood.  At OOPSLA/ECOOP 90 there was an enlightening
episode one day when there was a morning panel on object-oriented vs
structured analysis and an afternoon session on frameworks.  In the morning
session, *no one* addressed the issue of reusability, and in the afternoon
session, no one had any methodology for designing frameworks of
reusable components (beyond the insight that the process is iterative).

So, by talking about components rather than just reusability, we suggest
that this is the correct way to think about software at various levels
of abstraction (and that there is more to the story).  By talking about
reusability, however, we only point to an abstract goal that is very
hard to realize in practice.  We are still looking for the right view
of software components that will actually give us the degree of
reusability that we seek.

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Dr. O.M. Nierstrasz                 | Tel:    41 (22) 787.65.80
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