Extended Chomsky-Schützenberger theorems
The operations of a homomorphic equality and an inverse homomorphic equality are introduced. These operations are obtained from n-tuples of homomorphisms, incorporating the notion of an equality set. For one-tuples they are a homomorphism and an inverse homomorphism. Homomorphic equality and inverse homomorphic equality operations provide simple and uniform characterizations of the recursively enumerable sets in terms of the regular sets, and of classes H(L λ MR) in terms of L. These characterizations resemble the Chomsky-Schützenberger theorem for context-free languages.
KeywordsSmall Class Input String Canonical Extension Input Tape Formal Language Theory
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