astronomy

Jorma Rissanen

Jorma Rissanen is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Jorma Rissanen rather than just read about it. In short: Jorma Johannes Rissanen (October 20, 1932 – May 9, 2020) was an information theorist, known for originating the minimum description length (MDL) principle and practical approaches to arithmetic coding for lossless data compression. His work inspired the development of the theory of stochastic chains with memory of variable length.

Key takeaways

Jorma Rissanen belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Jorma Rissanen to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Jorma Rissanen from memory before moving on to harder problems.

Reference excerpt

Jorma Johannes Rissanen (October 20, 1932 – May 9, 2020) was an information theorist, known for originating the minimum description length (MDL) principle and practical approaches to arithmetic coding for lossless data compression. His work inspired the development of the theory of stochastic chains with memory of variable length.

Education and career Rissanen was born in Pielisjärvi (now Lieksa) 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, 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. from the Helsinki University of Technology in 1965 with a topic on adaptive control theory. He then moved to IBM Almaden in San Jose, California and stayed with IBM until his retirement in 2002, with a brief interruption in 1974 as a professor of control theory at Linköping University in Sweden. During that time, he became familiar with the work on algorithmic randomness by Andrey Kolmogorov and Per Martin-Löf, which inspired his work on arithmetic coding 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 and a fellow of Helsinki Institute for Information Technology.

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 in 1998, the Kolmogorov Medal of the University of London in 2006, and the IEEE Claude E. Shannon Award in 2009. A Festschrift collection, which includes an interview and substantial biographical information, was published by the Tampere University of Technology in honor of his 75th birthday.

Personal life Rissanen married Riitta Åberg in 1956, and they have a son Juhani and a daughter Natasha.

Bibliography Rissanen, Jorma (1989). Stochastic complexity in statistical inquiry. Singapore: World Scientific. ISBN 981-238-549-5. OCLC 52854741. Cybenko, George; O'Leary, Dianne P.; Rissanen, Jorma, eds. (1999). The mathematics of information coding, extraction, and distribution. New York: Springer. ISBN 0-387-98665-0. OCLC 39922074. Rissanen, Jorma (2007). Information and complexity in statistical modeling. New York: Springer. ISBN 978-0-387-68812-1. OCLC 232363255. Rissanen, Jorma (2012). Optimal estimation of parameters. Cambridge: Cambridge University Press. ISBN 978-1-139-51850-5. OCLC 796796345.

References

External links Professor Jorma Rissanen page at RHUL Grünwald, Peter; Myllymäki, Petri; Roos, Teemu; Tabus, Ioan (September 2020). "In Memoriam: Jorma J. Rissanen (1932-2020)" (PDF). IEEE Information Theory Society Newsletter. pp. 13–14. Retrieved October 3, 2022.

Worked examples

Example 1 — a first encounter with Jorma Rissanen

Start with the simplest possible case. Write down what Jorma Rissanen claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Jorma Rissanen before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Jorma Rissanen ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Jorma Rissanen

In research: Jorma Rissanen appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Jorma Rissanen in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Jorma Rissanen is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1932 births, 2020 deaths, Aalto University alumni, so understanding it makes those chapters shorter.
In everyday life: Look for Jorma Rissanen outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Jorma Rissanen in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Jorma Rissanen means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Jorma Rissanen out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Jorma Rissanen in simple terms?

Why does Jorma Rissanen matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Jorma Rissanen?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Jorma Rissanen.