Definition: A model of computation proposed by A. K. Chandra, L. Stockmeyere, and D. Kozen, which has two kinds of states, AND and OR. The definition of accepting computation is adjusted accordingly.

See also time/space complexity, Turing machine.

Note: First proposed as a model for parallel computation, it has been widely used to prove complexity bounds on problems.

Author: SKS

More information

A. K. Chandra and L. J. Stockmeyer, Alternation, pages 98-108, and D. Kozen, On Parallelism in Turing Machines, pages 89-97, both in Proc. Seventeenth Annual IEEE Symposium on Foundations of Computer Science, 1976.

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Entry modified 14 December 2005.
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Cite this as:
Sandeep Kumar Shukla, "alternation", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed. 14 December 2005. (accessed TODAY) Available from: