It is now more than one year ago that I took over the very honorable responsibility of being Editor-in-Chief of Acta Informatica, which is one of the oldest journals dedicated to Theoretical Computer Science (TCS) and rooted in Germany. In fact, the journal was founded more than 50 years ago, and to the best of my knowledge, the only TCS journal rooted in Germany that predated Acta Informatica was Elektronische Informationsverarbeitung und Kybernetik, later renamed as Journal of Information Processing and Cybernetics, but this journal ceased to exist in the early 1990s.

The reputation of Acta Informatica not only stems from its long history, but also from the scientific impact of the publications that appeared in this journal. For instance, Róbert Szelepcsényi published The method of forced enumeration for nondeterministic automata with Acta Informatica in 1988, which let him win the prestigious Gödel Prize in 1995 (together with Neil Immerman).

Such a long history also means changes over time on the Editorial Board.

First, I have to say thanks to my predecessor, Prof. Dr. Dr. h. c. Christel Baier. She served as Editor-in-Chief for 8 years. She managed to maneuver this journal through the difficult times we all faced.

Then, I have to thank Prof. Dr. Leah Epstein from Haifa University, Israel, for serving on the Editorial Board (EB) since 2015; she decided to leave the EB in the beginning of this year.

Also, thanks to Prof. Dr. Prakash Panangaden from McGill University, Canada, who left the EB after serving us since 2014.

Finally, big thanks to Prof. Dr. Ernst-Rüdiger Olderog from Oldenburg University, Germany, who decided to leave the EB after his retirement. He was actually Editor-in-Chief of Acta Informatica between 2000 and 2014 as the predecessor of Christel Baier.

Conversely, we have a number of new people who entered the EB in the last months. We very much welcome their addition and hope that this move will broaden the visibility, but also the topical and geographical breadth of Acta Informatica in the future.

We like to introduce these new EB members in this Editorial in alphabetical order, omitting academic titles for convenience.

  • Akanksha Agrawal, Indian Institute of Technology Madras, India. She mainly works in parameterized algorithms and complexity, often in connection with graph algorithms and computational geometry.

  • Johannes Blömer, Paderborn University, Germany. He works in information security and cryptography, but also in other modern areas of computer science, like clustering and learning algorithms (foundations of Artificial Intelligence), as well as quantum computing and complexity.

  • Serge Gaspers, The University of New South Wales, Australia. He also works in parameterized algorithms and complexity, but also (besides graph algorithms) with a strong focus on foundations of Artificial Intelligence, in particular, connections to computational aspects of logic.

  • Artur Jeż, University of Wrocław, Poland. He works on string combinatorics and string processing, including applications in data compression. He is also very knowledgeable in formal language theory in general.

  • Ralf Klasing, CNRS, LaBRI, Université de Bordeaux, France. His research focuses on the design and analysis of algorithms in general and on distributed and approximation algorithms, as well as on combinatorial and graph algorithms more specifically.

  • Dominik Koeppl, University of Yamanashi, Japan. He works on lossless data compression and compressed text indices, but also more generally on string processing algorithms.

  • Yoshio Okamoto, The University of Electro-Communications, Japan. He works in computational geometry, combinatorial reconfiguration and in graph algorithms, but also, more generally, in combinatorial optimization.

  • Uéverton Souza, Universidade Federal Fluminense (UFF), Brazil. His fields of work and expertise include algorithmic graph theory, parameterized algorithms, computational complexity, including fine-grained complexity, and combinatorics in general.

  • Frank Stephan, National University of Singapore. He has a particularly broad research background, ranging from algorithmic questions to areas like computational learning theory, complexity and classical recursion theory.

  • José Verschae, Pontificia Universidad Católica de Chile. His research interests include combinatorial optimization and integer programming theory, approximation and online algorithms, scheduling theory, and network design.

  • Mingsheng Ying, Chinese Academy of Sciences and Tsinghua University, China. His research interests are quantum computation, programming theory, and foundations of artificial intelligence, but he also has a deep background in process calculus of concurrent programs.

  • Binhai Zhu, Montana State University, USA. He works in string algorithms, computational biology, computational geometry, and combinatorial optimization in general.

This list indicates that there have been a number of changes concerning the EB of Acta Informatica. We hope that these changes will help attract further high-quality submissions to this journal and cover more modern aspects of Theoretical Computer Science, which is clearly also important for the future standing of our journal. Then, it can not only boast of an honorable history but also look forward into a bright future.

Further changes pertain to the technological aspects of Acta Informatica, including the transition from the submission system Editorial Manager to Springer's own editorial system SNAPP that is still under development.

Conversely, there are also (technically speaking) invariants of Acta Informatica. Quite in general, I have to thank all EB members that are faithfully serving on the EB for many years, or even many decades. Without all their dedicated work, this journal would long have ceased to exist. For instance, Prof. Dr. Manfred Broy from TU Munich, Germany, was Editor-in-Chief from 1982 until 2000 and is still on the EB. To give another example, Prof. Dr. Erol Gelenbe from Imperial College London, United Kingdom, was member of the EB since 1979 and also still belongs to the EB of Acta Informatica.

But clearly one name is sticking out here, and this is the name of Prof. Dr. Dr. h.c. mult. Arto Salomaa. We are very proud to be able to congratulate him on serving on the Editorial Board of Acta Informatica now for more than 50 years, starting his work on the EB in 1973, shortly after the journal came into being. This is truly a unique and remarkable achievement.

I am not aware of any other person having served on any Editorial Board over five decades.

Arto can boast with a long and successful international research career that was always well rooted in his home town Turku, Finland. It was also in Turku where I first met Arto in person, three decades ago. Back then, Arto was chairing the conference Developments in Language Theory, or DLT for short, a conference series that actually started in those days (initiated by Arto) and returned to Scandinavia this year for its 27th edition, after its beginnings exactly thirty years ago. It was quite fascinating to see him (and others) who one actually knew long before from all the textbooks that have been written in particular by Arto. I am also not aware of any other person in Theoretical Computer Science who has (co-)authored nearly fifty textbooks in this area. Also, after his retirement in 1999, Arto continued to publish many research articles.

His achievements also implied that in 2001, he became an Academician of the Academy of Finland. This is particularly remarkable as there are only twelve living persons admitted this title, across all disciplines, see https://www.aka.fi/en/about-us/scientists-behind-the-research/academicians-of-science/.

Arto is also member of the Academia Europea, see https://www.ae-info.org/ae/Member/Salomaa_Arto. There, one can also find one of the many passions of Arto, that of describing anecdotes and his own encounters with great scientists, see https://www.ae-info.org/ae/Member/Salomaa_Arto/Highlight. This also proves how well Arto is connected within the whole history of Theoretical Computer Science as we can see it today.

We really wish Arto all the best for the future, also in view of the fact that he is expecting his 90th anniversary in early summer, 2024.

Finally, I would also like to thank all the Associate Editors and the members of the EB and of the editorial department of Acta Informatica for their help in this period of transition. We all hope to steer this journal through safer waters in the coming years.