Jorma Johannes Rissanen (October 20, 1932 – May 9, 2020) was an

information theorist Information theory is the scientific study of the quantification, storage, and communication of information. The field was originally established by the works of Harry Nyquist and Ralph Hartley, in the 1920s, and Claude Shannon in the 1940s. ...

, known for originating the

minimum description length Minimum Description Length (MDL) is a model selection principle where the shortest description of the data is the best model. MDL methods learn through a data compression perspective and are sometimes described as mathematical applications of Occa ...

(MDL) principle and practical approaches to

arithmetic coding Arithmetic coding (AC) is a form of entropy encoding used in lossless data compression. Normally, a string of characters is represented using a fixed number of bits per character, as in the ASCII code. When a string is converted to arithmetic ...

for

lossless data compression Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statistic ...

. His work inspired the development of the theory of

stochastic chains with memory of variable length Stochastic chains with memory of variable length are a family of stochastic chains of finite order in a finite alphabet, such as, for every time pass, only one finite suffix of the past, called context, is necessary to predict the next symbol. The ...

Education and career

Rissanen was born in

Pielisjärvi Pielisjärvi is a former municipality in the region of North Karelia in Finland. The municipality had inhabitants in 1970. Pielisjärvi was a Finnish-speaking municipality. Pielisjärvi municipality was joined with the city of Lieksa in 197 ...

(now

Lieksa Lieksa () is a town and municipality of Finland. It is located in the North Karelia region. The municipality has a population of () and covers an area of of which is water. The population density is . The municipality is unilingually Finnish. ...

in Finland and grew up in Kemi, a border town between Finland and Sweden. He moved to Helsinki and studied at the

Helsinki University of Technology Helsinki University of Technology (TKK; fi, Teknillinen korkeakoulu; sv, Tekniska högskolan) was a technical university in Finland. It was located in Otaniemi, Espoo in the metropolitan area of Greater Helsinki. The university was founded in ...

, where he obtained his Master’s degree in electrical engineering in 1956 and licentiate in control theory in 1960. He studied there under Olli Lokki and Hans Blomberg. Rissanen became an IBM researcher since 1960, first in Stockholm, Sweden, while still a Ph.D. student under Hans Blomberg. Most of his PhD work was done remotely as a result and he received his

Ph.D. A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is ...

from the

in 1965 with a topic on adaptive control theory. He then moved to IBM Almaden in

San Jose, California San Jose, officially San José (; ; ), is a major city in the U.S. state of California that is the cultural, financial, and political center of Silicon Valley and largest city in Northern California by both population and area. With a 2020 popu ...

and stayed with IBM until his retirement in 2002, with a brief interruption in 1974 as a professor of control theory at

Linköping University Linköping University (, LiU) is a public research university based in Linköping, Sweden. Originally established in 1969, it was granted full university status in 1975 and is one of Sweden's largest academic institutions. The university has fou ...

in Sweden. During that time, he became familiar with the work on algorithmic randomness by

Andrey Kolmogorov Andrey Nikolaevich Kolmogorov ( rus, Андре́й Никола́евич Колмого́ров, p=ɐnˈdrʲej nʲɪkɐˈlajɪvʲɪtɕ kəlmɐˈɡorəf, a=Ru-Andrey Nikolaevich Kolmogorov.ogg, 25 April 1903 – 20 October 1987) was a Sovi ...

and

Per Martin-Löf Per Erik Rutger Martin-Löf (; ; born 8 May 1942) is a Swedish logician, philosopher, and mathematical statistician. He is internationally renowned for his work on the foundations of probability, statistics, mathematical logic, and computer scie ...

, which inspired his work on

and MDL, leading to a stream of ground-breaking publications from the late 1970s to the early 1990s. The work on MDL developed into the more general notions of stochastic complexity (about which he wrote an influential book) and universal coding/modeling. After retirement from IBM, he remained professor emeritus of

Tampere University of Technology Tampere University of Technology (TUT) ( fi, Tampereen teknillinen yliopisto (TTY)) was Finland's second-largest university in engineering sciences. The university was located in Hervanta, a suburb of Tampere. It was merged with the University o ...

and a fellow of

Helsinki Institute for Information Technology Helsinki Institute for Information Technology HIIT ( fi, Tietotekniikan tutkimuslaitos HIIT, sv, Forskningsinstitutet för informationsteknologi HIIT) is a joint research unit of two leading research universities in Helsinki, Finland, the Universi ...

Awards and recognitions

He was awarded the IEEE Richard W. Hamming Medal in 1993, an IEEE Golden Jubilee Award for Technological Innovation from the

IEEE Information Theory Society The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...

in 1998, the

Kolmogorov Andrey Nikolaevich Kolmogorov ( rus, Андре́й Никола́евич Колмого́ров, p=ɐnˈdrʲej nʲɪkɐˈlajɪvʲɪtɕ kəlmɐˈɡorəf, a=Ru-Andrey Nikolaevich Kolmogorov.ogg, 25 April 1903 – 20 October 1987) was a Sovi ...

Medal of the

University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degree ...

in 2006, and the IEEE Claude E. Shannon Award in 2009. A

Festschrift In academia, a ''Festschrift'' (; plural, ''Festschriften'' ) is a book honoring a respected person, especially an academic, and presented during their lifetime. It generally takes the form of an edited volume, containing contributions from the h ...

collection, which includes an interview and substantial biographical information, was published by the

in honor of his 75th birthday.Peter Grünwald, Petri Myllymäki, Ioan Tabus, Marcelo Weinberger, and Bin Yu (eds.)
Festschrift in Honor of Jorma Rissanen on the Occasion of his 75th Birthday
Tampere University of Technology, 2008.

Personal life

Rissanen married Riitta Aberg in 1956, and they have a son Juhani and a daughter Natasha.

Bibliography

* * * *

References

External links

Professor Jorma Rissanen
page at RHUL * 1932 births 2020 deaths People from Lieksa Information theorists Coding theorists Finnish computer scientists Finnish mathematicians IBM employees Aalto University alumni Linköping University faculty {{Compu-scientist-stub