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From: hawksk@lonex.radc.af.mil (Kenneth B. Hawks)
Newsgroups: comp.software-eng
Subject: Re: Provocative statement
Message-ID: <1991Apr26.124442.6553@lonex.radc.af.mil>
Date: 26 Apr 91 12:44:42 GMT
References: <9776@castle.ed.ac.uk> <1991Apr25.133216.20855@jyu.fi>
Organization: Rome Laboratory, Griffiss AFB, New York
Lines: 30

In article <1991Apr25.133216.20855@jyu.fi> sakkinen@jytko.jyu.fi (Markku Sakkinen) writes:
writes:
>
>If the bridge designer wants to have a greater security factor,
>(s)he can specify a little thicker steel and cables than suggested
>by standard calculations.  The software designer cannot say:
>"This system has to be really safe and secure, so let's put in
>30% more code!"
>
I must respectfully DISAGREE!   If a software engineer wants a "safer"
                                              ^^^^^^^^
program, then standard safety components should be incorporated into the
algorithm implemented.  For example, using a table look-up method in lieu
of calculating the Tangent of 90 degrees.  This accomplishes two things,
the algorithm executes faster, and the processor cannot "hang" trying to
compute infinity.  Other "safety" measures can include such 'standard'
techniques as looking at all input variables for range accuracy and 
reasonableness prior to using them.  Checking ones' answer, can also be
accomplished.    30% more code?   Maybe.  Nuclear release, and weapon
system navigation software must have _designed_in_ safety features. 

After 26 years of software development for aerospace systems, believe me
that there are lots of solid, standard "safety" components that are
applicable.  The fundamental premise I have always advocated is, "each
program must be engineered to solve the problem at hand."

Kenneth B. Hawks                                   |\   /|   "Fox Forever"
Rome Laboratory, Griffiss AFB, NY                   ^o.o^
hawksk@lonex.radc.af.mil                            =(v)=
Disclaimer:  There is no one else here who thinks like I do; therefore....