Arto Salomaa (1934-2025)#
Arto Salomaa was elected as Member of the Informatics section in 1992. Professor Erol Gelenbe, the Chair of the Informatics section writes:"Arto Salomaa, whom I met at the early "Switching and Automata Theory" conferences in the late sixties when I was preparing my Master's and then PhD in the USA on automata theory, is a towering figure in theoretical computer science and one of the earliest computer scientists of the “Mathematics and Informatics Section” of Academia Europaea. I had the pleasure to read and cite his work, as well as the work of his student, Paavo Turakainen. His loss is deeply felt by many of our Members, and his influence will remain permanently in the fundamental concepts and achievements of our field."
Tribute to Arto Salomaa#
A Towering Figure in Theoretical Computer Science#
This is an excerpt from the preface to a special issue of Theoretical Computer Science (track C) honoring
Arto Salomaa.
Arto Salomaa passed away on January 26, 2025. He was a world-class Finnish mathematician and
theoretical computer scientist, renowned for his foundational contributions to automata theory, formal
languages, and numerous other areas within theoretical computer science. His work profoundly shaped
the mathematical foundations of the field and inspired generations of researchers.
His scientific career was truly international. As a graduate student, he received a scholarship to Berkeley,
where he attended J. Myhill’s automata theory seminar, which deeply influenced him. Upon returning to
his home institution, the University of Turku, he established a research group in automata theory that
became internationally renowned and continues to be active today, more than half a century later.
In the late 1960s, Arto spent three years at what became his second academic home, the University of
Western Ontario in Canada. During this time, his first book, Theory of Automata, was published, marking
the beginning of his extraordinary career as an author of scientific books. Shortly thereafter, he
published his iconic monograph Formal Languages, a highly influential work that cemented his status as
a pioneering figure in the field. Over the years, Arto authored more than ten highly influential scientific
monographs. Some were masterful explorations of their respective topics, while others introduced or
promoted novel areas of study, including formal power series, L-systems, public-key cryptography, and
DNA computing. In collaboration with Grzegorz Rozenberg, Arto co-authored a comprehensive
treatment of formal languages. This monumental work, the Handbook of Formal Languages, spans three
volumes and over 2,000 pages, serving as a definitive reference in the field.
Beyond being an exceptionally original and creative researcher who continually explored new directions,
Arto was also a leading educator in theoretical computer science. The remarkable clarity of his
mathematical writing introduced many scientists to formal languages and automata theory, and his
texts became fundamental to the education of multiple generations of researchers. Also, many of the
Ph.D. students he guided went on to become prominent scientists worldwide, further demonstrating his
profound impact as an educator and mentor.
Arto served three five-year terms as an Academy Professor of the Academy of Finland, the highest
academic position in the country. In 2001, the Academy of Finland awarded him the title of
Academician, a prestigious honor granted to only 12 individuals in the sciences nationwide.
He was a highly decorated scientist, a testimony to his prestige within the international scientific
community. Arto was the recipient of nine honorary degrees and a distinguished member of several
esteemed institutions, including the Finnish Academy of Science and Letters, the Finnish Society of
Science and Letters, Academia Europaea, and the Hungarian Academy of Science as foreign member.
His achievements were recognized with numerous prestigious awards, such as the Prize of the
Foundation for Finnish Culture, the Magnus Ehrnrooth Prize of the Finnish Society of Science and
Letters, the European Association for Theoretical Computer Science Award, the Finnish Professor of the
Year award, the Nokia Foundation Prize, and the title of Honorary Professor of the Al.I.Cuza University in
Romania. In his honor, the Developments in Language Theory Symposium series has introduced the
prestigious annual Arto Salomaa Prize.
Arto made significant contributions to the scientific community. For instance, he played a key role in the
establishment and early development of the European Association for Theoretical Computer Science,
where he served as president from 1979 to 1985. Also, he was an active member of numerous editorial
boards for prestigious academic journals and book series, further shaping the field through his expertise
and leadership.
We, the editors and contributors, express our deep sorrow at Arto’s passing. Each of the editors had the
privilege of a warm and special friendship with him. We will miss him immensely and remain grateful for
his presence in our lives and the profound influence he had on us.
Juhani Karhumäki MAE, Turku, Finland
Jarkko Kari, Turku, Finland
Lila Kari, Waterloo, Canada
Hermann Maurer MAE, Graz, Austria
Ion Petre, Turku, Finland
Grzegorz Rozenberg MAE, Leiden, The Netherlands and Boulder, Colorado, USA
February 2025
