Archive for November 2013

Niklaus Wirth birthday symposium, 20 February, Zurich

In honor of Niklaus Wirth’s 80-th birthday we are organizing a symposium at ETH on February 20, 2014. This is a full-day event with invited talks by:

  • Vint Cerf
  • Hans Eberlé
  • Michael Franz
  • me
  • Carroll Morgan
  • Martin Odersky
  • Clemens Szyperski
  • Niklaus Wirth himself

From the symposium’s web page:

Niklaus Wirth was a Professor of Computer Science at ETH Zürich, Switzerland, from 1968 to 1999. His principal areas of contribution were programming languages and methodology, software engineering, and design of personal workstations. He designed the programming languages Algol W, Pascal, Modula-2, and Oberon, was involved in the methodologies of structured programming and stepwise refinement, and designed and built the workstations Lilith and Ceres. He published several text books for courses on programming, algorithms and data structures, and logical design of digital circuits. He has received various prizes and honorary doctorates, including the Turing Award, the IEEE Computer Pioneer, and the Award for outstanding contributions to Computer Science Education.

Participation is free (including breaks, lunch and the concluding “Apéro”) but space is strictly limited and we expect to run out of seats quickly. So if you are interested (but only if you are certain to attend) please register right away.

Symposium page and access to registration form: here.

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New paper: alias calculus and frame inference

For a while now I have  been engaged in  a core problem of software verification: the aliasing problem. As with many difficult problems in science, it is easy to state the basic question: can we determine automatically whether at a program point p the values of two reference expressions e and f can ever denote the same object?

Alias analysis lies at the core of many problems in software analysis and verification.

Earlier work [2] I introduced an “alias calculus”. The calculus is a set of rules, attached to the constructs of the programming language, to compute the “alias relation”: the set of possibly aliased expression pairs. A new paper [1] with Sergey Velder and Alexander Kogtenkov improves the model (correcting in particular an error in the axiom for assignment, whose new version has been proved sound using Coq) and applies it to the inference of frame properties. Here the abstract:

Alias analysis, which determines whether two expressions in a program may reference to the same object, has many potential applications in program construction and verification. We have developed a theory for alias analysis, the “alias calculus”, implemented its application to an object-oriented language, and integrated the result into a modern IDE. The calculus has a higher level of precision than many existing alias analysis techniques. One of the principal applications is to allow automatic change analysis, which leads to inferring “modifies clauses”, providing a significant advance towards addressing the Frame Problem. Experiments were able to infer the “modifies” clauses of an existing formally specied library. Other applications, in particular to concurrent programming, also appear possible. The article presents the calculus, the application to frame inference including experimental results, and other projected applications. The ongoing work includes building more efficient model capturing aliasing properties and soundness proof for its essential elements.

This is not the end of the work, as better models and implementations are needed, but an important step.


[1] Sergey Velder, Alexander Kogtenkovand Bertrand Meyer: Alias Calculus, Frame Calculus and Frame Inference, in Science of Computer Programming, to appear in 2014 (appeared online 26 November 2013); draft available here, published version here.
[2] Bertrand Meyer: Steps Towards a Theory and Calculus of Aliasing, in International Journal of Software and Informatics, Chinese Academy of Sciences, 2011, pages 77-116, available here.


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The biggest software-induced disaster ever


In spite of the brouhaha surrounding the Affordable Care Act, the US administration and its partisans seem convinced that “the Web site problems will be fixed”.

That is doubtful. All reports suggest that the problem is not to replace a checkbox by a menu, or buy a few more servers. The analysis, design and implementation are wrong, and the sites will not work properly any time soon.

Barring sabotage (for which we have seen no evidence), this can only be the result of incompetence. An insurance exchange? Come on. Any half-awake group of developers could program it over breakfast.

Who chose the contractors?

When the problems first surfaced a few weeks ago, anyone with experience and guts would have done the right thing: fire all the companies responsible for  the mess and start from scratch with a dedicated, competent and well-managed team.

The latest promises published are that by the end of the month “four out of five” of the people trying to register will manage to do it. Nice. Imagine that when trying to make a purchase at Amazon you would succeed 80% of the time.

And that is only an optimistic goal.

The people building the site do not have infinite time. In fact, the process is crucially time-driven: if people do not get health coverage in time, they will be fined. But what if they cannot get coverage because the Web sites do not respond, or mess up?

Consider for a second another example of another strictly time-driven project: on January 1, 2002, twelve countries switched to a common currency, with the provision that their current legal tender would lose its status only a bare two months later. The IT infrastructure had to work on the appointed day. It did. How come Europe could implement the Euro in time and the US cannot get a basic health exchange to work?

Here is a possible scenario: the sites do not work (cannot handle the load, give inconsistent results). A massive wave of protests ensues, boosted by those who were against universal health coverage in the first place. Faced with popular revolt and with the evidence, the administration announces that the implementation of the universal mandate — the enforcement of the fines — is delayed by a year. In a year much can happen; opposition grows and the first exchanges are an economic disaster since the “young healthy adults” feel no pressure to enroll. The law fades into oblivion. Americans do not get universal health care for another generation. Show me it is not going to happen.

The software engineering lessons here are clear: hire competent companies; faced with a complicated system, implement the essential functions first, but stress-test them; deploy step by step, with the assurance that whatever is deployed works.

The exact reverse strategy was applied. As a result, we face the prospect of a software disaster that will dwarf Y2K and other famous mishaps; a disaster that software engineering textbooks will feature for decades to come.


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Informatics education in Europe: Just the facts


In 2005 a number of us started Informatics Europe [1], the association of university departments and industrial research labs in computer science in Europe. The association has now grown to 80 members across the entire continent; it organizes the annual European Computer Science Summit and has published a number of influential reports. The last one just came out: Informatics Education in Europe: Institutions, Degrees, Students, Positions, Salaries — Key Data 2008-2012 [2]. The principal author is Cristina Pereira, who collected and organized the relevant data over more than a year; I helped with the preparation of the final text.

At the beginning of Informatics Europe we considered with particular attention  the model of the Computing Research Association [3], which played a crucial role in giving computer science (informatics) its due place in the US academic landscape. Several past and current officers of the CRA,  such as Willy Zwaenepoel, Ed Lazowska, Bob Constable, Andy Bernat, Jeannette Wing, Moshe Vardi and J Strother Moore gave keynotes at our early conferences and we of course asked them for the secrets of their organization’s success. One answer that struck us was the central role played by data collection. Just gathering the  facts, such as degrees and salaries, established for the first time a solid basis for serious discussions. We took this advice to heart and the report is the first result.

Gathering the information is particularly difficult for Europe given the national variations and the absence of centralized statistical data. Even the list of names under which institutions teach informatics in Europe fills a large table in the report. Cristina’s decision was, from the start, to favor quality over quantity: to focus on impeccable data for countries for which we could get it, rather than trying to cover the whole continent with data of variable credibility.

The result is the first systematic repository of basic information on informatics education in Europe: institutions, degrees offered and numbers awarded, student numbers, position titles and definitions, and (a section which will not please everyone) salaries for PhD students, postdocs and professors of various ranks.

The report is a first step; it only makes sense if we can regularly continue to update it and particularly extend it to other countries. But even in its current form (and with the obvious observation that my opinion is not neutral)  I see it as a major step forward for the discipline in Europe. We need an impeccable factual basis to convince the public at large and political decision-makers to give informatics the place it deserves in today’s educational systems.


[1] Informatics Europe site, see here.

[2] Cristina Pereira and Bertrand Meyer: Informatics Education in Europe: Institutions, Degrees, Students, Positions, Salaries — Key Data 2008-2012, Informatics Europe report, 30 September 2013, available here.

[3] Computing Research Association (US), see here.


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