Władysław M. Turski 1 2 It Was Fun While It Lasted.

1 Władysław M. Turski

Władysław M. Turski 2

It Was Fun

While It Lasted


It Wasn't Much Fun

1959, Moscow (USSR), M.Sc. Thesis

I was a computer


It Was Fun

1960, Manchester (UK), Mercury

When love prevails

Logic fails

So the computer

Was made neuter


It Was Fun

Computing meteor stream orbits


It Was Fun

Running simulations of meteor swarm’s evolution


It Was a Mistake

I thought the computer was for computing

(Just as Aristotle thought brain was for cooling blood)


But it took me long time to see the light

First I thought computers were too difficult to program



So I wrote compilers

KLIPA, ALGOL-60



Then I thought running programs on computers was too messy



So I wrote an operating system

SODA



Then I thought something was

amiss with the data



So I played with data structuresSo I played with data structures


And I’ve sinned

For five long years I worked in the industry.

Directing the transfer of OS/360 to Polish-made RIAD computers.


Much later (1983, Dublin)

Responding to an invited paper I said:

Fred Brooks is a hard act to follow: I know, I’ve lifted the OS/360 !


Then I thought I saw the light

Computer is for executing programs!


Programming methodology

Structured programming

(programming structures)

GOTO considered harmful



Step-wise refinement

Correctness



Correctness, yes but what does it mean?

With respect to ...



Correctness wrt formal specification

- „faultily faultless”

- clear, but useless



Specs

Reality Program

Correctness?

Ill-defined relationship



Theory

Model Model

SatisfactionSatisfaction

Well-defined relationship


I was sure I saw the light

It all reduces to theories.

A good theory leads to good programs and satisfied customers.

A poor theory hinders construction of good programs and makes customers weep.



Build theories of small domains, make program-models for them, then combine theories and programs shall jell together!



But it ain’t necessarily so!

• combining theories is difficult (and not always possible)

• combining implementations is (nearly always) messy and often dangerous



I thought that perhaps combinig little actions into larger systems should be done entirely without any notion of „time”, i.e even without any predetermined notion of „follows”.



Thus the concept of doubly guarded command

)( rearactionfront

was born and (partially) explored


But while I followed the light

The world was changing

became the soup du jour


In the new brave world

Computers,

becoming ever more numerous (and physically smaller),

disappear behind services they provide.



Computation has to be correct.

Service has to be dependable.



The mathematical, strict

criterion of correctness

is being replaced

by a behavioural, loose

criterion of dependability.



All actors (people, machines and systems thereof) occasionally malfunction.

This is not only accepted, but also expected.



No-one really complains that Windows is prone to crash,

only that it crashes at an inopportune moment.



Like no-one complains

that tires occasionally go flat,

only that it happens when we are particularly short of time.



No-one is to blame and the guilt is subtly shifted to the „user”:

If I only didn’t drive there, if I only didn’t press these two keys together!

Or was it three?



Every hour more users than babies are born.

Each user soon becomes an expert at their specific fingering.

Such an expertise quickly becomes an article of faith and an academic discipline.



Particular fingerings turned articles of faith cum academic disciplines are invested.


An aside, from Webster’s:

invest

- to array in the symbols of office and honor

- to furnish with power or authority

- to surround with troops or ships so as to prevent escape or entry

- to commit money in order to earn a financial return



In the ecumenical primordial ocean of Internet,

growth is primarily by accretion of external grime.

Reason is yet to be born: while no-one convinces, many try to catch.



Correctness, rigour, mathematics of computing is pushed into an ever smaller and darker corner labelled

„special concerns”.


I have the feeling that

Having witnessed the birth of computing science,

I am witnessing its demise.


While it lasted

It certainly was fun!

43 Władysław M. Turski

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Władysław M. Turski 1 2 It Was Fun While It Lasted.

Documents

messy slide

data slide

harmful slide

explored slide

useless slide

jour slide

dangerous slide

neuter slide