Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!tut.cis.ohio-state.edu!purdue!varnau
From: varnau@cs.purdue.EDU (Steve Varnau)
Newsgroups: comp.software-eng
Subject: Re: Information Systems is an Engineering Discipline
Message-ID: <8160@medusa.cs.purdue.edu>
Date: 4 Oct 89 02:04:25 GMT
References: <1142@svx.SV.DG.COM> <34399@regenmeister.uucp> <5296@eos.UUCP> 
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Reply-To: varnau@cs.purdue.edu (Steve Varnau)
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Organization: Department of Computer Science, Purdue University
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In article  ejp@abvax.icd.ab.com (Ed Prochak) writes:
>
>Eugene,
>	I agree with you for the most part. I think you hinted at the
>key difference between software and hardware: model building, based on
>known mathematical fact. For example, aircraft designers can build a
>scale model and test its characteristics at a very low cost compared
>to the final product. They make use of Reynolds number and other
>aerodynamic parameters to be sure the model will behave like the
>real thing.
>	We need a rule for scaling software so that we can test
>small, cheap models of the software system. 
     [deleted text]

Here at Purdue University, I attended a talk about "Software Windtunnels"
by Dr. D. Comer.  In this talk he explored ways to test software (or 
software development methods) in ways similar to airplanes.  He even
used analogies to the Reynolds number.  (Which is a dimensionless number.)
All physics equations are homogeneous in their units, i.e. they are 
algebraically the same on both sides of the equal sign.  (I can't recall
the exact term he used for this concept.)  Software engineering hasn't 
discovered this concept, or at least any equations using it yet.  He seemed
to think we should work on this and that scale factors could be found.

On another topic (software safety), everyone is blaming errors on design,
but many systems have been around so long that they no longer resemble
the system designed.  Has anyone considered preventative maintenance?  People
compare software reliability to bridge reliability.  Even bridges fall down
when they are not maintained (i.e. NYC is having this problem in a big way).


-- 
Steve Varnau  =  varnau@medusa.cs.purdue.edu
Purdue University, West Lafayette, IN     (Software Engr. Research Center)
IBM, Poughkeepsie, NY