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Janusz Brzozowski (computer scientist)

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Alma mater  Princeton University
Education  Princeton University
Known for  Brzozowski derivative
Fields  Computer Science

Name  Janusz Brzozowski
Role  Computer scientist
Notable students  Imre Simon
Janusz Brzozowski (computer scientist) mavericuwaterloocabrzozojohnlargegif

Born  May 10, 1935Warsaw, Poland (1935-05-10)
Thesis  Regular Expression Techniques for Sequential Circuits (1962)
Books  Asynchronous circuits

Doctoral advisor  Edward J. McCluskey

Janusz (John) Antoni Brzozowski (born on May 10, 1935 in Warsaw, Poland) is a Polish-Canadian computer scientist.


In 1962, Brzozowski earned his PhD in the field of electrical engineering at Princeton University under Edward J. McCluskey. The topic of the thesis was Regular Expression Techniques for Sequential Circuits. From 1967 to 1996 he was Professor at the University of Waterloo. He is known for his contributions to mathematical logic, circuit theory, and automata theory.

Achievements in research

Brzozowski worked on regular expressions and on syntactic semigroups of formal languages. The result was Characterizations of locally testable events written together with Imre Simon, which had a similar impact on the development of the algebraic theory of formal languages as Marcel-Paul Schützenberger's characterization of the star-free languages.

In the area, there are today at least three concepts bearing Brzozowski's name in honour of his contributions: The first is the Brzozowski conjecture about the regularity of noncounting classes. Second, Brzozowski's algorithm is a conceptually simple algorithm for performing DFA minimization. Third, Eilenberg's reference work on automata theory has a chapter devoted to the so-called Brzozowski hierarchy inside the star-free languages, also known as dot-depth hierarchy. Curiously, Brzozowski was not only co-author of the paper that defined the dot-depth hierarchy and raised the question whether this hierarchy is strict, he later also was co-author of the paper resolving that problem after roughly ten years. The Brzozowski hierarchy gained further importance after Thomas discovered a relation between the algebraic concept of dot-depth and the alternation depth of quantifiers in first-order logic via Ehrenfeucht-Fraïssé games.

He received the following academic awards:

  • NSERC Scientific Exchange Award to France (1974–1975)
  • Japan Society for the Promotion of Science Research Fellowship (1984)
  • Distinguished Professor Emeritus, University of Waterloo, Canada (1996)
  • Medal of Merit, Catholic University of Lublin, Poland (2001)
  • Canadian Pioneer in Computing (2005)
  • Research papers

  • J. A. Brzozowski: Derivatives of regular expressions, Journal of the ACM 11(4): 481–494 (1964)
  • J. A. Brzozowski, I. Simon: Characterizations of Locally Testable Events, FOCS 1971, pp. 166–176
  • R. S. Cohen, J. A. Brzozowski: Dot-Depth of Star-Free Events. Journal of Computer and System Sciences 5(1): 1-16 (1971)
  • J. A. Brzozowski, R. Knast: The Dot-Depth Hierarchy of Star-Free Languages is Infinite. Journal of Computer and System Sciences 16(1): 37–55 (1978)
  • Books

  • J. A. Brzozowski, M. Yoeli: Digital Networks. Prentice–Hall, 1976
  • J.A. Brzozowski, C.-J. H. Seger: Asynchronous Circuits. Springer-Verlag, 1995
  • References

    Janusz Brzozowski (computer scientist) Wikipedia