After nine years, Jos Baeten will step down as general director of CWI on 30 September 2020 and there will be a retirement symposium in his honour on 1 October 2020. (Jos Baeten's successor will be Tom de Kok. You can read the CWI news item related to Tom de Kok's appointment here. Tom de Kok, just like Jos Baeten before him, joins CWI from Eindhoven University of Technology.)
Jos Baeten has been one of the prime movers in the development of process algebra since 1987, and has been the driving force behind the CONCUR conference series and the CONCUR Basic Research Actions in the late 1980s and the early 1990s. Apart from being general director of CWI, he has served the TCS community in a variety of roles and organisations, and has helped to connect the work of the concurrency-theory community with that done in control and mechanical engineering. He has also supervised more than 30 PhD theses.
I asked Jos a few questions via email and I am happy to share his answers with the readers of this blog. Thanks to Jos for all the contributions he has given to the research community throughout his career, and for sharing his opinions and reminiscences with us!
Luca: Let's start from the beginning. If I remember correctly, your background was in model theory. Could you tell us what prompted you to move to doing research in computer science?
Jos: I have a Master in logic and foundations of mathematics (with a minor in philosophy) from Utrecht University, with a Master’s thesis on lambda calculus, and a PhD in logic and foundations of mathematics from the University of Minnesota, with a PhD thesis on definability theory (a cross between recursion theory and set theory) entitled "Filters and ultrafilters over definable subsets of admissible ordinals". Returning from the US, I got a job teaching undergraduate maths at Delft University. But I wanted getting into research, and meeting Jan Bergstra he said there were lots of opportunities in computer science research, not in maths. Writing a paper with him and Jan Willem Klop on term rewriting systems would qualify me, he said. So it happened, and I got a postdoc at CWI in the framework of the ESPRIT I project. I kept on doing maths, but it was called computer science.
Luca: I have heard that you were recruited by Jan Bergstra and Jan Willem Klop to work within their group at the CWI, and that Rob van Glabbeek joined the team soon after you. Could you tell us about the environment at the CWI at that time? It must have been a very exciting place to be with all the activity related to work on ACP and related topics.
Jos: It was a heady period. The group of Jan and Jan Willem was expanding rapidly on EU money, with me, Rob van Glabbeek and Frits Vaandrager. I really liked ACP and doing universal algebra.
Luca: What was your first paper in CS about? Which paper from your initial period at the CWI are you most proud of?
Jos: My first paper was "On term rewriting, Term rewriting systems with priorities". I am most proud of my first ACP paper, "Syntax and defining equations for an interrupt mechanism in process algebra". This is about adding the priority operator. For axiomatisation, it needed an auxiliary operator that later turned out to be almost optimal. I came up with an axiomatisation, and Jan Bergstra forced me to prove it correct by doing all the critical pairs. I found a small error in pair 101 (of the 102 pairs), corrected it and proved the result correct. This all in a couple of weeks.
Luca: Let's move on to the CONCUR project: How did it come about and what was its legacy? I recall that you came to visit Matthew Hennessy at the University of Sussex when I was a PhD student there to discuss the CONCUR proposal. How did you become involved in leading such a large and high profile group of researchers so early in your career at the CWI? What was it like to lead the CONCUR project?
Jos: This is again due to Jan Bergstra: he believes in delegating responsibilities quickly. When the new instrument of Basic Research Action came up in the EU, he wanted a BRA with Hoare, Milner and Hennessy. I got the assignment and made a trip to the UK visiting all three, and got all of them on board. The idea of the project was unification, but that did not come about, everyone kept doing their own thing. We did, however, produce excellent papers, including the curious
J.C.M. Baeten, J.A. Bergstra, C.A.R. Hoare, R. Milner, J. Parrow & R. de Simone, The variety of process algebra. Deliverable ESPRIT Basic Research Action 3006, CONCUR, University of Edinburgh 1991
Luca: How would you summarize the history of the conference CONCUR? Can it be split into different periods, and if so, what characterizes them?
Jos: CONCUR 90, which was the first CONCUR conference, was organised by BRA CONCUR, but with speakers from all 5 BRA’s in the area of concurrency; in 1991 Milner did not want such a conference to occur in Edinburgh, so Jan Bergstra and I did it again in Amsterdam. Then, we involved Scott Smolka for 1992 and after that, it was established, with a steering committee comprised of representatives from the 5 BRAs and Scott. As of 1993, it was firmly established, we found a niche and time period (end of August, beginning of September). All branches of concurrency were involved from the start, and over the years, it shows fashion clearly, for instance in certain years there was a lot of pi-calculus.
Luca: In the 80s and the 90s there were three "schools" in process algebra, the ACP, CCS, and CSP schools. With the benefit of hindsight, which were heir main contributions? To which extent have they converged? Is this classification still important for current research?
Jos: I refer to my paper
J.C.M. Baeten, A brief history of process algebra. Theoretical Computer Science 335 (2/3), 2005, pp. 131-146.
I do a comparison in there. In my opinion, the book
J.C.M. Baeten, T. Basten and M.A. Reniers, Process Algebra: Equational Theories for Communicating Processes. Cambridge Tract in Theoretical Computer Science 50, Cambridge University Press 2010
has the unification, presenting all three in the same framework. However, process algebra is out of fashion, so who cares?
Luca: When did you become interested in supervisory control? What motivated you to apply techniques from process algebra in that research field? Looking at the outcome of that work, both in theory and in practice, that was a very good move! Could you tell us about the position you had in Mechanical Engineering? How did it come about and what was it like to work in that department?
Jos: More than 20 years in the department of computer science, having been dean twice, I got to know the university very well indeed. Koos Rooda, professor of systems engineering at Mechanical Engineering, requested my assistance to get more software engineering into systems engineering, to replace his cooperation with Martin Rem, who became rector. In particular, he was interested in the combination of discrete event reasoning (i.e., process algebra) with the continuous mathematics of systems and control. Having done process algebra with timing and probabilities, I was willing to take up this challenge. Upon his retirement, with the vigorous backing of the dean of Mechanical Engineering at the time, I took over his position. At mid-life, I was ready for a change. I liked the hands-on attitude of mechanical engineering students, who are no good at theory or proofs, but are very good in using mathematics and trying out software tools. But then, I was asked to apply to the vacancy of director of CWI. This was the job I had always wanted. I had enjoyed being dean and doing research management, and CWI is a very prestigious institute with (at that time) very independent management.
Luca: Back at CWI: What skills do you think one needs to be the director of such a high-profile institute? What was your vision for the CWI and how much of it did you manage to achieve? What role do you think the CWI can/should have in the coming decade and beyond?
Jos: The most important skill is hiring those early career scientists that grow out to become top scientists. Internally, you have to manage your key personnel, operating by consensus and compromise. Externally, you have to find your way in national science politics and always justify your existence. The growing tension between Dutch universities and Dutch extra-university research institutes has almost defeated me, but I managed to complete my term until retirement, and leave CWI in good shape, to my opinion. I managed to keep the excellent reputation of the institute, and also managed to bring in dynamics, rejuvenation and new subjects. What I did not achieve, is that CWI again becomes a publisher, and publishes diamond journals.
Luca: You have played a role in organizations such as the EATCS, ERCIM and IFIP. Do you think that such societies still play a role today? How do think they should evolve to fulfill their mission?
Jos: I do, but they have to keep evolving if they want to stay relevant. It is a pity that the EATCS could not take a role in the open access movement (you certainly made a very good effort!). I think ERCIM is doing ok, but not great. IFIP, I think, has become irrelevant.
Luca: You have been a strong supporter of open access. What is your opinion of the state of play in open access and what do you think we could do to move forward?
Jos: Progress is slow but exists. I am a strong advocate of Plan S, that has really set some things in motion. A key point is that it looks like we can achieve immediate green, and still allow all researchers to submit articles wherever they want. I do not like the way it is going with transformative agreements, you'd think that by now, publishers would be putting all their efforts to become sellers of data analytics services.
Acknowledgements: I thank Javier Esparza, the chair of the CONCUR Steering Committee, for contributing some the questions to Jos.