!!!My links and thanks to the IBM Vienna Lab
Cliff B Jones\\
February 18, 2018


[{Image src='1-cliff.gif' caption='Photo: Archive Cliff' alt='Cliff Jones' width='140' class='image_left' height='205' popup='false'}]
In April 1968, I attended a course in the Vienna Lab on the Operational
Semantic description of the PL/I programming language ("ULD"). It was
a beautiful spring week and, as well as thoroughly enjoying the course, I fell
in love with the city - but I had no idea at the time just how big an impact
the city, Lab and colleagues would have on my life.


Before that fateful April, I had been heavily involved in testing the first
compiler for PL/I in IBM's Hursley Lab. A large number of test cases had
been written and we supplemented them with a tool that automatically
generated random "executable" programs. At some point in time, enough
test cases ran that the decision was made to ship the PL/I F compiler to
customers. I'll confine myself to saying that the product was not perfect.


I was convinced (long before I heard Edsger Dijkstra's biting aphorism
about testing) that a quality product could only be achieved if the design
process was sound. Sadly this was not widely accepted in IBM: one senior
US manager maintained "give me a FORTRAN compiler and enough PL/I
test cases, and I'll give you a PL/I compiler". My hope was that a formal
description of a programming language could be used as the basis for a sound
design process for a compiler.


My week in Wien not only introduced me to their semantic description
method, I found that [Peter Lucas|Biographien/Lucas,_Peter] was already reasoning about equivalence
between formal semantic models. I also took long walks every morning and
on one of these I recall seeing a workman stop the traffic - yes, even the
''Straßenbahn'', to let a duck lead its ducklings across the Ringstraße. This
was a city in which I felt life had a sensible balance and a place where I wanted to
live.


Returning to my home location, I set about trying to fix an assignment
to Vienna. In October 1968, I arrived at the start of a two year assignment
to the Vienna Lab.


Adjusting to Viennese life was not completely ''problemlos''. I remember
[Heinz Zemanek|Biographien/Zemanek,_Heinz] asking me whether I had found it easy to settle in and I don't
think my "not entirely" was the wished-for answer. However, the plusses
vastly outweighed the negatives. My parents had been neither academic nor
musical. Vienna opened the window to opera, ''Lieder'' and, thanks to Hans
Bekic, ''Hausmusik''.


Professionally, in that first sojourn in Wien, my main collaborations
were with Peter Lucas and Wolfgang Henhapl. Hans was away for one of
the two years working with Peter Landin in London. I attended my first
IFIP working group when WG 2.2 held a meeting in Vienna. This was a
scene changing event: Scott met Strachey, Tony Hoare spoke (I believe for
the first time) about his axiomatic approach. Back in the Lab we were
trying to understand Bob Floyd's "Assigning meaning to programs" paper
and after some debate it was decided to invite Dana Scott to see if he could
help us. Fortunately, he ignored our stated purpose and turned up with a
manuscript on which he and Jaco de Bakker had been working!


By the time I left Vienna for the first time in 1970, we had clearly
established that it was ''possible'' to reason about a compiler design based on a
"ULD" description of the source language; but we were also convinced that
many facets of such descriptions introduced gratuitous difficulties. Peter,
Hans and I exchanged letters on ways to circumvent these problems and
the extent to which denotational semantics would provide a better basis.


Back in the Hursley Lab, I did some more work on a "functional" language
semantics but also turned my attention to the development of normal (non
compiler) programs. Many of the ideas of what most people think of as
VDM come from this time (e.g. relational post conditions, data reification).
Late in 1972, Peter Lucas called me at our home in Wilshire and explained 
that the Vienna Lab had the chance to develop the PL/I compiler
for IBM's new ""FS" machines. My recollection is that I said "yes" before he
actually asked if I'd return to Wien! This time I took a "permanent transfer" 
and became a full member of IBM Austria. The Lab was still located
at Parkring 10 but we had acquired the third as well as the fifth 
foors. 

We actually moved back to Vienna when our son Peter was only weeks old. The
technical story of the denotational semantics description which got 
christened "VDM" has been told in other places. As Heinz Zemanek became
ever more involved in IFIP, 
[Kurt Walk|Infos_zum_AF/Editorial_Board/Walk,_Dr._Kurt_(Angewandte_Informatik,_Organisation)] 
took over as Lab director.
Then FS machine was cancelled! The Lab began to haemorrhage its
key people. Strenuous efforts were made to set up a new mission for the
Vienna Lab. For me this included trips to Paris - sometimes with Heinz
or with Kurt Bandat. 

I was one of the last to go in that period of diaspora
and when I left, I predicted that the Lab would survive only for a very
short time because of its high "loaded manpower rate". It is to Kurt Walk's
credit that he proved my time estimates overly pessimistic but in the end
the Lab did die. One of Dines Bjorner's and my proudest joint achievements
is rescuing the scientific ideas behind VDM first with the help of Springer
Verlag (LNCS 61) and subsequently revising this for a book in Prentice-Hall's 
famous red-and-white series.


I moved to IBM's European Systems Research Institute. After this, I
found another man who was prepared to back his personal judgement and
accept a high school dropout with no qualifications - Tony Hoare got me
into Oxford to pursue a belated doctorate.


The Vienna Lab provided a wonderful environment. Above all, the colleagues were superb (I dare not attempt to list them all for fear that I forget
someone). Sadly, too many of them have "shuffeld off this mortal coil" far
too early. The loss of Hans Bekic hit me soon after taking up my first chair
at Manchester - again Springer helped record some of what might have
otherwise been lost (LNCS 177).
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[{Image src='6-cliff 75 Markt Obersdorf.jpeg' caption='Cliff at Marktobersdorf 1975, Photo: Private archive' alt='Cliff Jones' height='350' class='image_block' width='450'}]
[{Image src='cliff-kudiela-neu-85.jpeg' caption='Cliff Jones with Kudielka and Neuhold 1985, Photo: Private archive' alt='Members of Lab' height='350' class='image_block' width='519'}]
[{Image src='2-Logic-Lounge_Cliff-B-Jones_by_Nadja-Meister.jpg' caption='In Logic Lounge 2016 with former Vienna IBM members\\Photo: Nadja Meister. March 2016' alt='Members of Lab' height='300' class='image_block' width='559'}]
[{Image src='4-lucas-Bekic.jpeg' caption='Lucas and Bekic, two of the main driving forces of VDM, Photo: Private archive' alt='Lucas and Bekic Jones' height='300' class='image_block' width='416'}]
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!PS:  It might interest some readers that I have recently been working with a PhD student (Troy Astarte) on the history of Formal Semantics - one output of this effort is a comparison of four formal descriptions of ALGOL 60. See [An Exegesis of Four Formal Descriptions of
ALGOL 60|https://assets.cs.ncl.ac.uk/TRs/1498.pdf].


















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