From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] design issues in operating systems
From: anothy@cosym.net
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Message-Id: <20011203160800.D526A1998A@mail.cse.psu.edu>
Date: Mon,  3 Dec 2001 11:07:49 -0500
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// There's merit in evolution, which adjusts to changing
// conditions, whereas design needs to be predictive.

why are people talking about design and evolution as though
they're mutually exclusive?

the plan 9 kernel was, i believe, designed, but it has certainly
evolved since the first edition (witness the rift between the
file server kernel and the cpu/terminal kernel). we've seen a
number of different graphics models in Plan 9, and i believe
each of them was designed, but it may also make sense to
talk about them as evolutions of each other, based on what
practical application in differing environments shows to be
better or worse - like natural selection. note the movement
of image memory between kernel and userland and the
movement of the IP stack (if i'm remembering these right).

a good design is one which is simple enough to comfortably
allow for reasonable evolution. whereas i agree design _is_
predictave, the results need not be static.
ア