Abstract
We show that level 3/2 of the dot-depth hierarchy is decidable. More precisely, we identify a pattern \(\mathbb{B}\) such that the following holds: If F is a deterministic finite automaton that accepts L, then L belongs to level 3/2 of the dot-depth hierarchy if and only if F does not have \(\mathbb{B}\) as a subgraph in its transition graph. The latter condition can be tested in nondeterministic logarithmic space.
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A preliminary version of this paper was presented at the conference STACS 2000.
C. Glaßer supported by Studienstiftung des Deutschen Volkes.
H. Schmitz supported by Deutsche Forschungsgemeinschaft (DFG), grant Wa 847/4-1.
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Glaßer, C., Schmitz, H. Languages of Dot-Depth 3/2. Theory Comput Syst 42, 256–286 (2008). https://doi.org/10.1007/s00224-007-9002-0
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DOI: https://doi.org/10.1007/s00224-007-9002-0