Winner of the 2022 Alonzo Church Award

The 2022 Alonzo Church Award for Outstanding Contributions to Logic and Computation is given to Dexter Kozen for for his fundamental work on developing the theory and applications of Kleene Algebra with Tests, an equational system for reasoning about iterative programs.

The ACM Special Interest Group on Logic (SIGLOG), the European Association for Theoretical Computer Science (EATCS), the European Association for Computer Science Logic (EACSL), and the Kurt Goedel Society (KGS) are pleased to announce that Dexter Kozen has been selected as the winner of the 2022 Alonzo Church Award for Outstanding Contributions to Logic and Computation for his fundamental work on developing the theory and applications of Kleene Algebra with Tests, an equational system for reasoning about iterative programs, published in:

 Dexter Kozen. Kleene Algebra with Tests. ACM Transactions on Programming Languages and Systems 19(3): 427-443 (1997). DOI: 10.1145/256167.256195

The Contribution

This work on Kleene Algebra with Tests (KAT) is one of the high points among remarkable contributions of Dexter Kozen to logics of programs. It is a culmination of a series of articles by Dexter Kozen that define and apply KAT, an equational system that combines Kleene Algebra (the algebra of regular expressions) with Boolean Algebra (the tests). Together, the terms of the two algebras are capable of representing while programs, and their combined equational theory is capable of proving a wide range of important properties of programs. Although reasoning in KAT under arbitrary commuting conditions is undecidable, Kozen observes that when the commuting conditions are limited to including tests, it is decidable and in PSPACE. He illustrates the power of KAT with these decidable commuting conditions by proving a well-known folk theorem: Every while program can be simulated by a program with just one loop. KAT has been successfully applied to a variety of problems over the past 25 years, including modeling and reasoning about packet-switched networks.

The 2022 Church Award was selected by a jury consisting of Thomas Colcombet, Mariangiola Dezani, Javier Esparza, Radha Jagadeesan (chair), and Igor Walukiewicz.

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