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Closure properties of hyper-minimized automata

Published online by Cambridge University Press:  14 November 2011

Andrzej Szepietowski*
Affiliation:
Institute of Informatics, University of Gdańsk, ul. Wita Stwosza 57, 80-952 Gdańsk, Poland.. matszp@inf.ug.edu.pl
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Abstract

Two deterministic finite automata are almost equivalent if they disagree in acceptanceonly for finitely many inputs. An automaton A is hyper-minimized if noautomaton with fewer states is almost equivalent to A. A regular languageL is canonical if the minimal automaton accepting L ishyper-minimized. The asymptotic state complexitys(L) of a regular languageL is the number of states of a hyper-minimized automaton for a languagefinitely different from L. In this paper we show that: (1) the class ofcanonical regular languages is not closed under: intersection, union, concatenation,Kleene closure, difference, symmetric difference, reversal, homomorphism, and inversehomomorphism; (2) for any regular languages L1 andL2 the asymptotic state complexity of their sumL1 ∪ L2, intersectionL1 ∩ L2, differenceL1 − L2, and symmetricdifference L1 ⊕ L2 can be boundedbys(L1s(L2).This bound is tight in binary case and in unary case can be met in infinitely many cases.(3) For any regular language L the asymptotic state complexity of itsreversal LR can be bounded by2s(L). This bound is tightin binary case. (4) The asymptotic state complexity of Kleene closure and concatenationcannot be bounded. Namely, for every k ≥ 3, there exist languagesK, L, and M such thats(K) = s(L) = s(M) = 1ands(K) = s(L·M) = k.These are answers to open problems formulated by Badr et al.[RAIRO-Theor. Inf. Appl. 43 (2009) 69–94].

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Type
Research Article
Copyright
© EDP Sciences 2011

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References

Références

Badr, A., Geffert, V. and Shipman, I., Hyper-minimizing minimized deterministic finite state automata. RAIRO-Theor. Inf. Appl. 43 (2009) 6994. Google Scholar
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