Today, let's talk about responsibility and
accountability. The University of Houston's College
of Engineering presents this series about the
machines that make our civilization run, and the
people whose ingenuity created them.
Never is planning a bigger
headache than it is when we design software to
control large computer electronic systems. It's
very hard to design a system along with its
software. They depend on each other. They must grow
together. Yet they're created by quite different
people.
Trouble starts when the government writes contracts
with software designers. We spell out just how the
software will look, years in the future. That way,
we expect to get just what we pay for, with no
padding or fudging.
We call that the waterfall model, because work
cascades down from one stage to the next. The
pieces are supposed to mesh with the certainty of
gravity. Of course they never do. With tedious
regularity, we get bad software, cost overruns, and
both.
The problem arises in the very nature of planning.
Good planning has to see the process, not just the
end. It has to include means for changing itself as
the work unfolds. It has to anticipate its own
failures along the way.
Terrible trouble has followed software contracts
around. We had to shut down five nuclear reactors
in 1979. Their design software had been flawed. The
Therac-25 radiation therapy system killed five
patients with overdoses in the mid-'80s. The Hubble
Space Telescope was plagued with software problems.
So were the defensive electronics on the B1 bomber.
An alarmed congressional committee has pointed the
finger at procurement thinking. I've worked under
such contracts. I've had to fill out countless
timelines in proposals. By April I'll design the
apparatus. I'll build it by July. I'll collect the
data by Thanksgiving and analyze them during
Epiphany. Just try doing original work that way!
No sensible parent makes his child absolutely
accountable. The result would be an absolutely
irresponsible child. Procurement people are slow to
see that. They forget process in the rush to
guarantee results.
Good design is an interaction among responsible
people. The trick is to rough something out -- then
interact and correct. Software has to evolve with
hardware. We must spiral in on a good design, says
Science magazine writer Mitchell
Waldrop. You cannot specify anything good and new
before you create it.
Big over-specified systems are too hard to fix when
they break down. Our procurement system itself is
like bad software. Maybe it should be replaced. We
need a system that will attract designers who want
to be responsible -- not just accountable.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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