Saturday, September 30, 2006

N is a Number

Yesterday, ICE-TCS hosted its first movie event with the projection of the documentary film N is a Number: A Portrait of Paul Erdös by George Csicsery. I bought the DVD of this award winning documentary using my Springer author discount, and, rather than watching it at home, I decided to share it with my colleagues at Reykjavík University. I also hoped that some of our students would show up to watch the documentary. (Every opportunity is good to entice students to study TCS! Unfortunately, however, no student took the bait and joined us :-()

The documentary is good and I recommend it, even though it does not hold many surprises for people who have read the popular books on Paul Erdös. However, watching Paul Erdös strut his skills on the dias before diving into the mathematics was an enjoyable experience for somebody like me who never had the chance of seeing him "live".

I wonder whether he is still managing to keep the SF's score low wherever he may be now.

Addendum: The Erdös numbers of the members of ICE-TCS are here.

Sunday, September 24, 2006

MohammadReza Mousavi in Reykjavík

Albeit belatedly, due to some last minute bureacratic hassles arising from the lack of experience of the staff at a young university like Reykjavík University, MohammadReza Mousavi has joined our little concurrency theory group at Reykjavík University. Anna and I are understandably thrilled at having him here. Mohammad will have a joint position between Reykavík University and TU Eindhoven.

The 'group' has doubled in size since August this year, with the arrival of Silvio Capobianco (a mathematician from Rome) and Mohammad. Their arrival has also strengthened ICE-TCS considerably, and their presence is giving Anna and me a good intellectual environment to work in. Now it's up to us to make the most of this opportunity, and I hope that we'll be able to capitalize on their scientific strength. If we don't, then it's going to be solely our fault.

The problems we encountered in getting a visa for Mohammad at the last minute seem to have some positive consequences. Together with the Icelandic research council, we are pressing the politicians here to establish a fast-track for researchers seeking visas and work permits to come and work in Iceland. Having a "researcher visa" procedure might make it more attractive for scientists to come and work here in the North Atlantic, at times when access to other countries is becoming more and more difficult. I'll keep you posted on the developments.

Friday, September 22, 2006

New Perspectives on Fairness

I have just posted the concurrency column for the October 2006 installement of the Bulletin of the EATCS. The October column is a lovely piece entitled New Perspectives on Fairness by Daniele Varacca and Hagen Voelzer.

Fairness is an important concept that appears repeatedly in various forms in different areas of computer science, and plays a crucial role in the semantics and verification of reactive systems. Entire books are devoted to the notion of fairness---see, for instance, the monograph by Nissim Francez published in 1986---, and researchers in our community have painstakingly developed a taxonomy of various fairness properties that appear in the literature, such as unconditional fairness, weak fairness, strong fairness, and so on. This research is definitely important in light of the plethora of notions of fairness that have been proposed and studied in the literature.

But when is a temporal property expressing a fairness requirement? The authors of this column have recently developed a very satisfying answer to this fundamental question by offering three equivalent characterizations of ``fairness properties'' in the setting of linear-time temporal logic: a language-theoretic, a topological, and a game-theoretic characterization. This survey discusses these recent results in a very accessible fashion, and provides also a beautiful link between the study of fairness and classic probability theory.

I trust that you will enjoy reading this piece by Daniele and Hagen as much as I did. It is not often that one sees notions and results from several areas of mathematics and computer science combine so well to offer a formalization of a concept that confirms our intuition about it.

Tuesday, September 19, 2006

MacArthur Genius Awards for 2006

Lance Fortnow has a post on the latest batch of "genius awards" by the Mac Arthur foundation. Awards in disciplines of potential interest to the readers of this blog are to
  • Luis von Ahn.
  • Terence Tao.
  • Claire Tomlin. The announcement makes very interesting reading for a concurrency theorist, and for anyone interested in formal verification:
    Much of Tomlin's research concentrates on aeronautical applications of hybrid systems research, particularly aircraft flight control and air traffic conflict resolution. As the number of variables increases and their interactions become more complex, it becomes ever more difficult to guarantee that systems will always be within safe limits. Tomlin has developed practical algorithms for determining when unsafe conditions may arise, and for establishing feedback control laws for a hybrid system guaranteed to remain within a safe subset of all reachable states.
In keeping with my previous jazz-related post, I am glad to see that John Zorn, one of my favourite musicians and prime mover behind Tzadik Records, is one of the recipients of the award. Check out his Masada series if you have not done so already.

Congratulations to the winners of the awards!

Jazz meets Process Algebra

Bas Luttik's band, the Residence Jazz Sextet, now has a web site, and a CD. I heard a demo version of the CD, and it sounds good. On the band's web site, you can also listen to mp3 demos of the tracks on the CD. Enjoy it!

Saturday, September 16, 2006

An Essay by Palamidessi and Valencia

Catuscia Palamidessi and Frank Valencia have written an essay on Languages for Concurrency, which will appear in the Programming Languages column of the Bulletin of the EATCS (edited by Ian Mackie (Kings College, London, UK) and David Sands (Göteborg, Sweden)). I enjoyed reading it myself---even though I hopefully knew the material it covers already---, and warmly recommend it.

This essay is a commendable example of `outreach activity´ from two very active members of the concurrency theory community. Let's give it to our students and colleagues from other areas of computer science to read, and let's try to sow the seeds of our research area in our departments. Something good is bound to come out of these kind of efforts. For the moment, thanks to Catuscia and Frank for offering a contribution in this direction.

Thursday, September 14, 2006

New Award to Moshe Vardi

Moshe Vardi has been named as a co-recipient of the first LICS-test-of-time award for his paper An Automata-Theoretic Approach to Automatic Program Verification, co-authored with Pierre Wolper. Congratulations to Moshe and Pierre for yet another award!

See for a description of the award. I think that the idea to look back 20 years for the award is a good one, and look forward to seeing more awards in areas of logic related to concurrency theory and formal verification.

Experimental Blog for the IFIP WG on Concurrency Theory

Together with Wan Fokkink and Anna Ingolfsdottir, I recently set up a separate blog on concurrency theory. The aim of that blog is to serve as a dicussion forum for topics of interest to the members of IFIP WG1.8. I hope that the readers of this blog, if there are any, will contribute to the discussion threads that will be posted on the new blog.

Wednesday, September 06, 2006

PC Chair for FOSSACS 2008

FYI, the PC chair for FOSSACS 2008 will be Roberto Amadio. Sharpen your pencils and prepare good papers for that conference!

Tuesday, September 05, 2006

Gordon Plotkin is 60

On 7-8 September, LFCS, School of Informatics, University of Edinburgh, will host a symposium to celebrate Gordon Plotkin's 60th birthday. The detailed programme for that event lists a series of stellar speakers, and the list of participants is truly impressive.

This is really good to see. Gordon is one of the veritable giants in TCS, and he has had outstanding students and collaborators over the years. His contributions to the study of the semantics of programming languages (be it denotational, logical or operational) and to its mathematical underpinnings are well known, so I'll just limit myself to wishing Gordon a happy symposium.

Sunday, September 03, 2006

What Are the Most Important Open Problems in Concurrency?

Let us assume that one can assess the healthiness of a research field, say concurrency theory, by looking at the most important open problems in that field. These open problems can be used to try and convince researchers in another area and students that the field of concurrency theory is "alive and kicking", and maybe entice a few of them to work within the field.

Based upon this thought experiment, wouldn't it be a good thing to have a repository of open problems that identify the present state of development in concurrency theory, and suggest directions for further research?

At some point in the past, I started putting together a list of open problems, but I have not really maintained it for a while. Will you help me revive this enterprise by sending me, or posting as a comment to this blog entry, a description of your favourite open problems in concurrency theory, together with links to partial solutions and pointers to the literature? This input of yours might even form the basis for a useful installment of the Concurrency Column in the Bulletin of the EATCS, and generate a lot of research in our field following what Luca Trevisan has called in this very informative blog entry the "Hungarian approach to mathematics": pose very difficult problems, and let deep results, connections between different areas of math, and applications, come out as byproducts of the search for a solution.

By the way, Luca Trevisan has a few very interesting posts related to Szemeredi's theorem and other results in additive combinatorics. (See this one, and the five blog entries on Szemeredi's theorem.) Those posts give an inkling of the level of mathematical sophistication that has been reached in TCS research from the volume A camp. Check them out!