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From: craig@dcl-cs.UUCP
Newsgroups: comp.lang.ada,comp.lang.misc
Subject: Software Reuse  --  do we really know what it is ?
Message-ID: <371@dcl-csvax.comp.lancs.ac.uk>
Date: Thu, 18-Jun-87 04:46:36 EDT
Article-I.D.: dcl-csva.371
Posted: Thu Jun 18 04:46:36 1987
Date-Received: Sat, 20-Jun-87 09:25:12 EDT
References: <8706160502.AA26398@ucbvax.Berkeley.EDU>
Reply-To: craig@comp.lancs.ac.uk (Craig Wylie)
Distribution: world
Organization: Department of Computing at Lancaster University, UK.
Xref: utgpu comp.lang.ada:369 comp.lang.misc:440
List-Id: <comp.lang.ada>


There have been a couple of articles recently on Software Reuse and its
likely acceptance by Defence Contractors.  In considering Software Reuse in
general, not just with reference to Ada and DoD, do we know what it is ?
The scale of software that Ada allows the programmer to reuse seems to be
primarily that of the package (in Modula-2  the Module). Is this sufficient?
If we leave aside for the time being the question of whether Ada is an object
oriented language and accept that if it isn't then you can do a reasonably
good job faking it, reuse in Ada seems to be stuck at the level of the
Abstract data type. Furthermore the lack of any easy (or apparent) way to 
derive WHAT an Ada program is doing rather than HOW it is doing it ,
does put a large amount of the responsibility for recovering reusable
components on the programmer.

In summary I would like to offer a few statements for discussion
to see if we can clarify reuse.

1.	We don't really know what it is.

2.	It probably isn't a thing at all, but rather a collection of things
	depending on the scale at which the reuse is to take place.

3.	Languages such as Ada and Modula-2, and imperative languages in
	general are unsuitable for writing reusable software because of
	their concentration on the HOW rather than the WHAT.	

4.	Reuse of Design isn't considered at all by any current applications
	language.

5.	Nobody can force programmers to write good reusable code.

6.	Even if they do write reusable code how the **** do we ever find it
	again so that we can reuse it ?


All responses appreciated.

Craig.

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