Displaying similar documents to “Generalized pascal triangles: overview of new results”

Unambiguous recognizable two-dimensional languages

Marcella Anselmo, Dora Giammarresi, Maria Madonia, Antonio Restivo (2006)

RAIRO - Theoretical Informatics and Applications

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We consider the family UREC of unambiguous recognizable two-dimensional languages. We prove that there are recognizable languages that are inherently ambiguous, that is UREC family is a proper subclass of REC family. The result is obtained by showing a necessary condition for unambiguous recognizable languages. Further UREC family coincides with the class of picture languages defined by unambiguous 2OTA and it strictly contains its deterministic counterpart. Some closure and non-closure...

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....