It was fun

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(No Transcript)
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It Was Fun

• While It Lasted

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It Wasn't Much Fun
1959, Moscow (USSR), M.Sc. Thesis
I was a computer
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It Was Fun

• 1960, Manchester (UK), Mercury

When love prevails Logic fails So the computer
Was made neuter
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It Was Fun
Computing meteor stream orbits
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It Was Fun
Running simulations of meteor swarms evolution
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It Was a Mistake
I thought the computer was for computing
(Just as Aristotle thought brain was for cooling
blood)
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But it took me long time to see the light
First I thought computers were too difficult to
program
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But it took me long time to see the light
So I wrote compilers KLIPA, ALGOL-60
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But it took me long time to see the light
Then I thought running programs on computers was
too messy
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But it took me long time to see the light
So I wrote an operating system SODA
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But it took me long time to see the light
Then I thought something was amiss with the data
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But it took me long time to see the light
So I played with data structures
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And Ive sinned
For five long years I worked in the industry.
Directing the transfer of OS/360 to Polish-made
RIAD computers.
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Much later (1983, Dublin)
Responding to an invited paper I said
Fred Brooks is a hard act to follow I know, Ive
lifted the OS/360 !
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Then I thought I saw the light
Computer is for executing programs!
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Programming methodology
Structured programming
(programming structures)
GOTO considered harmful
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Programming methodology
Step-wise refinement
Correctness
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Programming methodology
Correctness, yes but what does it mean?
With respect to ...
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Programming methodology
Correctness wrt formal specification - faultily
faultless - clear, but useless
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Programming methodology
Specs
Correctness
?
Ill-defined relationship
Reality
Program
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Programming methodology
Theory
Satisfaction
Satisfaction
Well-defined relationship
Model
Model
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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.
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I was sure I saw the light
Build theories of small domains, make
program-models for them, then combine theories
and programs shall jell together!
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I was sure I saw the light

• But it aint necessarily so!
• combining theories is difficult (and not always
  possible)
• combining implementations is (nearly always)
  messy and often dangerous

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I was sure I saw the light
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.
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I was sure I saw the light
Thus the concept of doubly guarded command
was born and (partially) explored
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But while I followed the light
The world was changing
became the soup du jour
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In the new brave world
Computers, becoming ever more numerous (and
physically smaller), disappear behind services
they provide.
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In the new brave world
Computation has to be correct.
Service has to be dependable.
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In the new brave world
The mathematical, strict criterion of
correctness is being replaced by a behavioural,
loose criterion of dependability.
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In the new brave world
All actors (people, machines and systems thereof)
occasionally malfunction. This is not only
accepted, but also expected.
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In the new brave world
No-one really complains that Windowsâ is prone to
crash, only that it crashes at an inopportune
moment.
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In the new brave world
Like no-one complains that tires occasionally go
flat, only that it happens when we are
particularly short of time.
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In the new brave world
No-one is to blame and the guilt is subtly
shifted to the user If I only didnt drive
there, if I only didnt press these two keys
together!
Or was it three?
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In the new brave world
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.
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In the new brave world
Particular fingerings turned articles of faith
cum academic disciplines are invested.
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An aside, from Websters

• 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

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In the new brave world
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.
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In the new brave world
Correctness, rigour, mathematics of computing is
pushed into an ever smaller and darker corner
labelled special concerns.
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I have the feeling that
Having witnessed the birth of computing
science, I am witnessing its demise.
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While it lasted
It certainly was fun!
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