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From: orville@weyrich.UUCP (Orville R. Weyrich)
Newsgroups: comp.lang.ada,comp.software-eng
Subject: Re: Reserve Demobilization System Built Around Re
Message-ID: <1991Jun15.230328.1127@weyrich.UUCP>
Date: 15 Jun 91 23:03:28 GMT
References: <1991Jun11.062703.15671@netcom.COM> <PCG.91Jun14183250@aberdb.aber.ac.uk> <1991Jun14.152529.1@east.pima.edu>
Reply-To: orville@weyrich.UUCP (Orville R. Weyrich)
Organization: Weyrich Computer Consulting
List-Id: <comp.lang.ada>

In article <1991Jun14.152529.1@east.pima.edu> rharwood@east.pima.edu writes:
>In article <PCG.91Jun14183250@aberdb.aber.ac.uk>, pcg@aber.ac.uk (Piercarlo
>Grandi) writes:
>
>> Usually, I suspect, reuse is meant to be applied to the narrow case
>> where one does custom sw development, which is no longer the case in
>> most commercial installation; nearly everybody nowadays is using DBMSes
>> and enjoying the benefits of not reimplementing from scratch data
>> management programs.
>
>OK... maybe we can LIGHTLY (read as: "without flame") discuss and subsequently
>define what reuse really IS (or ought to be!).
>
>My Personal Opinion:  Calling a DBMS or GUI or math routine is NOT reuse. 
>Libraries of complex mathematical subroutines have been available to FORTRAN
>programmers since ENIAC, I suppose.  Perhaps "reuse" is truly short-hand for
>"source code reuse"?  The term has mostly come to represent the ability to
>incorporate software written for or funded by "some other" project with little
>or no modification; perhaps some customization (specifically, the instantiation
>of an Ada GENERIC unit for the target elements).  A major rewrite would be
>excluded frp

On the contrary, I would say that Calling DBMS, GUI, IMSL libraries, etc
are important examples of reuse. If these facilities were not available,
then people would be constantly re-implementing them. Perhaps these mundane
examples of reuse are taken for granted because they work so well.

This is not to say that there isin't great untapped potential for greater reuse.There is still a long way to go. There are several challenges involved in
increasing reuse:

	1) How to determine what is a candidate for reuse, and how to
	   package and describe it.

	2) How to find things that are available for reuse and which are
	   applicable to the problem at hand.

	3) How to glue together reusable fragments to form a coherent whole.

	4) How to create and use language features which facilitate reuse. 
	   (Examples include Ada generics, C++ multiple inheritance, ...).

	5) Legal questions like how to assure return on investment for those
	   who prepare software for reuse, and how to protect the initial
	   client from paying the entire development cost of a new reusable
	   component.

The current examples of reuse have successfully met these challenges. The
question remains, "what can we do for an encore?"



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Orville R. Weyrich, Jr., Ph.D.                   Certified Systems Professional
Internet: orville%weyrich@uunet.uu.net             Weyrich Computer Consulting
Voice:    (602) 391-0821                         POB 5782, Scottsdale, AZ 85261
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