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NY TIMES Friday, July 12, 1985
By Charles Mohr

SCIENTIST QUITS ANTIMISSILE PANEL, SAYING TASK IS IMPOSSIBLE

A computer scientist has resigned from an advisory panel on antimissle defense,
asserting that it will never be possibble to program a vast complex of battle
management computers reliably or to assume they will work when confronted
with a salvo of nuclear missiles.

The scientist, David L. Parnas, a professor at the University of Victoria in
Victoria, British Columbia, who is a a consultant to the Office of Naval Research
in Washington, was one of nine scientists asked by the Strategic Defense Initiative
Office to serve at $1,000 a day on the ``panel on computing in support of battle
management.''

Professor Parnas, an American citizen with secret military clearances, said in
a letter of resignation June 28 and in 17 pages of accompanying memorandums 
that it would never be possible to test realistically the large array of computers
that would link and control a system of sensors, antimissle weapons, guidance and 
aiming devices, and battle management stations.

Nor, he protested, would it be possible to follow orthodox computer program-
writing practices in which errors and ``bugs'' are detected and eliminated in
prolonged everyday use.

`Money spent will Be Wasted'
----------------------------

``Because of the extreme demands on the system and our inability to test it,
we wil never be able to believe, with any confidence, that we have succeded,''
he wrote.  ``Most of the money spent will be wasted.''

Comdr. James H. Offutt of the Navy, an official with the strategic defense office,
said in an interview Wednesday that it was ``probably true'' that what he called 
current techniques of writing computer programs would not be reliable, but he
added that Professor Parnas and other had been asked to explore new methods to
``unlock'' workable procedures.

``That is what S.D.I. is all about -- it is a reserach program'' said Commander
Offutt, who is deputy director for battle management, command, control and 
communications.  He said the goal was a ``realistic testing program'' and said he 
was convinced that this could be done through computer simulation of possible
events.

In his letter to Commander Offutt, Professor Parnas took note of President Reagan's
1983 request to the scientists to work toward making nuclear weapons obsolete and
impotent.

`No Technological Magic'
------------------------

``I believe,'' Professor Parnas said, ``that is is our duty, as scientists and
engineers, to reply that we have no technological magic that will accomplish
that.  The President and the public should know that.''

Professor Parnas, who worked full time at the Office of Naval Research from
1980 to 1982 and helped develop the battle computer program for the A-7 
fighter-bomber and other Navy systems, said that his objections were not
ideological and that he had no ``objections to weapons development in general.''

The professor, who grew up in New York City and previously taught at the University
of North Carolina, remains a consultant to the Navy.  In a telephone interview
Tuesday, he said he reached his conclusions about the program, widely known as a
``Star Wars'' plan, after attending the first meeting of the experts panel and 
after pondering the scientific dimensions of the antimissile problem.

The strategic defense office is hoping to spend $33 billion over six years for
research and testing on components of an antimissile defense, although Congress
cut $400 million from the request last year and is likely to cut at least $700
million this year.  Work has only begun on a design of defense.

Computers and the programs, or software, that control them are a vital element
in any defense.  They would be used to help space-based sensors detect and count
a hostile missile launching, sort decoys from warheads, calculate trajectories 
and track targets, aim directed energy or high-speed projectile weapons, assess
hits and misses and re-aim weapons and for other tasks.

In the interview, Professor Parnas said he thought it was impossible to believe
that the programs would be free of error or that they could meet the short ``hard''
deadlines inherent in a missile attack that might last only 30 minutes.

``The worst thing is that we wouldn't trust the system if we did build it,''
he remarked.

In his memorandums, the professor put forth detailed explanations of his doubts.
He argued that large-scale programs like that envisioned for the program 
require modifications based on realistic use, saying, ``It is only through such 
modifications that software becomes reliable.'' He contended this would never
be possible with the strategic missile defense.

He wrote at length about the possibilities, often discussed, that workable
programs could be written by computers themselves, or that ``artificial
intelligence'' could solve the problem or that programs could be adequately
verified through mathematical simulation.  In each case, he said he believed that
experience with such methods showed they were unrealistic as a solution.

Some other scientists have recently expressed public doubts that large-scale
programs free of fatal flaws can be written. Herbert Lin, a research fellow at
the Massachusetts Institute of Technology, said this month that the basic lesson
was that ``no program works the first time.''

Professor Parnas wrote to Commander Offutt, ``I am quite certain that you will
be able to find software experts who disagree with my conclusions.'' He said that
for many the antimissile program was seen as a ``pot of gold just waiting to
be tapped'' for research projects and also an exciting puzzzle that was ``fun
to work on,'' but that he had concluded the plan was not feasible.