Homomorphisms Preserving Trellis Languages
نویسنده
چکیده
It is proved that a homomorphism h preserves the class of languages recognized by trellis automata augmented with the capacity of handling the empty string (or, equivalently, generated by linear conjunctive grammars) if and only if either h is injective, or h maps every symbol to the empty string. The transformation is effective in the former case and cannot be effectively done in the latter.
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