The late Professor Leo Ojala studied digital technology as early as the beginning of the 1970s

Professor of Digital Technology Leo Ojala passed away recently at the age of 80. He retired from his professor’s duties in 2000, having been one of the first professors of computer science in Finland. Ojala graduated from the Department of Physics of Helsinki University of Technology in 1960. He worked in industry for some years and then moved back to the Department of Electrical Engineering, where he established a Digital Systems Laboratory while working as a laboratory engineer at the beginning of the 1970s.  He was appointed to the permanent post of Professor of Digital Systems in 1973.

The digital systems research group implemented many projects related to digital technology in cooperation with the industries, such as a vibration meter for the constructors of the Helsinki metro. At the same time, scientific publications of a high standard were written for Finnish and distinguished foreign journals.

• "In the beginning, our secretary typed the research papers using an IBM golf ball typewriter and we drew the formulas on them by hand. Ojala was extremely meticulous and therefore kept changing the text. We made new versions by cutting and gluing until one sheet of paper was as think as cardboard," says Nisse Husberg, who worked with Ojala from the beginning of the 70s.

The importance of digital circuits and microcomputers grew fast in the 1970s, more people became interested in the field, lecture halls filled up during digital technology courses and Ojala supervised more than 200 Master’s theses in the subject. 

After digital circuits and microcomputers, Ojala’s research focused on parallel and distributed systems and the theory of computation. One of the main research subjects were the Petri nets and their application when modelling different kinds of digital systems. Using analysers developed in research projects, it was possible to find out, for example, whether a system could deadlock due to a specific sequence of operations that would require restarting the system. The models help detect such mistakes early on in the planning stage.

Ojala was exceptionally internationally minded from as early as the 1970. He travelled to conferences a lot himself, followed the international scientific development in his field closely, and had an extensive library and collection of articles.

"It was natural for Ojala that the bar in research was always set to the highest international standards.  He also required this from his students, who he sent to the best international conferences of the field at an early stage of their careers. This was very exceptional at the time," says Ilkka Niemelä, who worked on his dissertation at Ojala’s laboratory at the end of the 1980s. 

"Ojala was known as a thinker. Even in seminars, he pondered matters in depth and challenged students," says Tomi Janhunen, who worked in Ojala’s laboratory in the 1990s before Ojala’s retirement.

In seminars organised by Ojala, participants familiarised themselves very thoroughly with the material, scientific articles and dissertations, by giving presentations and solving exercises in addition to the seminar. If the presenter did not quite seem to have understood something, Ojala sometimes interrupted the presentation and gave the person some additional material to have a look at. Usually, these pearls were then discussed again in the following seminar session.

"Ojala was very keen to order the most recent articles. When I was writing my dissertation on the logic of beliefs, the problematic of believing and knowing, and the conclusions made on the basis of beliefs, Ojala ordered a research paper on agents and their introspection for me based on the subject. There was just a slight problem – this particular article was in Japanese," Janhunen continues.

The theoretical side of computation was emphasised in the operation of the laboratory to such an extent that at the end of the 1990s, a decision was made to change the name of the laboratory to the Laboratory for Theoretical Computer Science.  At the time, the laboratory unit was still so small that everyone could easily sit around one coffee table, and the teaching focused on the subject matter and quality instead of the volume of students.

"A group of us could sit in Ojala’s office receiving assignments that were sometimes challenging. Although Ojala gave young colleagues demanding tasks, he accompanied them in polishing the required strategies and that way was in the background influencing and providing support in person," Janhunen adds.

Even after his retirement, Ojala was interested in future technologies. He was interested in the development of quantum computers in particular, although he no longer wrote scientific articles about them.

Photos: Tuomas Aura