Displaying similar documents to “Self-reproducing pushdown transducers”

The helping hierarchy

Patrizio Cintioli, Riccardo Silvestri (2001)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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Schöning [14] introduced a notion of helping and suggested the study of the class P help ( 𝒞 ) of the languages that can be helped by oracles in a given class 𝒞 . Later, Ko [12], in order to study the connections between helping and “witness searching”, introduced the notion of self-helping for languages. We extend this notion to classes of languages and show that there exists a self-helping class that we call SH which contains all the self-helping classes. We introduce the Helping hierarchy whose...

On the equivalence of linear conjunctive grammars and trellis automata

Alexander Okhotin (2004)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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This paper establishes computational equivalence of two seemingly unrelated concepts: linear conjunctive grammars and trellis automata. Trellis automata, also studied under the name of one-way real-time cellular automata, have been known since early 1980s as a purely abstract model of parallel computers, while linear conjunctive grammars, introduced a few years ago, are linear context-free grammars extended with an explicit intersection operation. Their equivalence implies the equivalence...

Translation from classical two-way automata to pebble two-way automata

Viliam Geffert, L'ubomíra Ištoňová (2010)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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We study the relation between the standard two-way automata and more powerful devices, namely, two-way finite automata equipped with some ℓ additional “pebbles” that are movable along the input tape, but their use is restricted (nested) in a stack-like fashion. Similarly as in the case of the classical two-way machines, it is not known whether there exists a polynomial trade-off, in the number of states, between the nondeterministic and deterministic two-way automata with ℓ nested pebbles....