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From: itcp@praxis.co.uk (Tom Parke)
Newsgroups: comp.software-eng
Subject: Re: Second System Effect
Message-ID: <1991Mar1.133951.29048@praxis.co.uk>
Date: 1 Mar 91 13:39:51 GMT
References: <30512@mimsy.umd.edu> <15369@megatest.UUCP> <1991Feb23.014111.16044@ico.isc.com>
Organization: Praxis, Bath, U.K.
Lines: 41

rcd@ico.isc.com (Dick Dunn) writes:

>pat@megatest.UUCP (Patrick Powers) writes:
>> In twelve years in the biz I haven't observed a second system effect.

>I think there must be some serious differences in understanding what is
>meant by "second system effect" - because in watching "the biz" for a
>longer time, I've seen very few pieces of commercial software in the past
>decade that *haven't* exhibited the second-system effect.  You can see it
>in most commercial UNIX systems, the X Window System, emacs, virtually all
>PC apps that have been around for a while.

Yup, second system effect, been there, done that, got burned.
(While in a previous employment I should point out.)

I will now do a typical net thing, post what I think is in the book
without having it to hand :-( sorry. But its that or not post.
Immodesty forbids etc...

As I recall the point Brooks is making is not that bells and whistles
get added to software - there are good reasons for this, see his "No
Silver Bullet" paper (IFIP '86, also published after that in ACM). 

The point is that on the first system we are conservative, and come
version 2 there is a lot of pent up "goodies we couldn't get in first
time round" and in the euphoria of "we've done it once we know how to
do it a second time" these are added to the spec without due and
proper consideration. The effect is a multitude of unforseen
interactions between these new features, substantial overruns, code
bloat, eventual panic.

The possible visible manifestation of this is not software encrusted
with features, but announced new versions of software that slip, and
slip... and when it arrives it's buggy, DBase IV is a likely candidate.

	Tom
-- 

Tom Parke (my opinions and spelling are strictly temporary) 
"UNIX - safe, when taken as directed."
itcp@praxis.co.uk