A Note on Two-Dimensional Probabilistic Finite Automata.
ABSTRACT This note introduces two-dimensional probabilistic finite automata (2-pfa's), and investigates several properties of them. We first show that the class of sets recognized by 2-pfa's with bounded error probability, 2-PFA, is incomparable with the class of sets accepted by two-dimensional alternating finite automata. We then show that 2-PFA is not closed under row catenation, column catenation, row +, and column + operations in Siromoney et al. (G. Siromoney, R. Siromoney, K. Krithivasan, Inform. and Control 22 (1973) 447).
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Conference Paper: A Survey on Picture-Walking Automata.[Show abstract] [Hide abstract]
ABSTRACT: Picture walking automata were introduced by M. Blum and C. Hewitt in 1967 as a generalization of one-dimensional two-way finite automata to recognize pictures, or two-dimensional words. Several variants have been investigated since then, including deterministic, non-deterministic and alternating transition rules; four-, three- and two-way movements; single- and multi-headed variants; automata that must stay inside the input picture, or that may move outside. We survey results that compare the recognition power of different variants, consider their basic closure properties and study decidability questions.Algebraic Foundations in Computer Science - Essays Dedicated to Symeon Bozapalidis on the Occasion of His Retirement; 01/2011
International Journal of Pattern Recognition and Artificial Intelligence 06/2000; 14:477-500. DOI:10.1142/S0218001400000313 · 0.56 Impact Factor
Conference Paper: A Space Lower Bound of Two-Dimensional Probabilistic Turing Machines.[Show abstract] [Hide abstract]
ABSTRACT: This paper shows a sublogarithmic space lower bound for two-dimensional probabilistic Turing machines (2-ptm’s) over square tapes with bounded error, and shows, using this space lower bound theorem, that a specific set is not recognized by any o(log n) space-bounded 2- ptm. Furthermore, the paper investigates a relationship between 2-ptm's and two-dimensional Turing machines with both nondeterministic and probabilistic states, which we call “two-dimensional stochastic Turing machines (2-stm’s)”, and shows that for any loglog n ≤ L(n) = o(log n), L(n) space-bounded 2-ptm’s with bounded error are less powerful than L(n) space-bounded 2-stm’s with bounded error which start in nondeterministic mode, and make only one alternation between nondeterministic and probabilistic modes.Developments in Language Theory, 6th International Conference, DLT 2002, Kyoto, Japan, September 18-21, 2002, Revised Papers; 01/2002