Some Uncountable Hierarchies of Formal Languages
نویسنده
چکیده
We consider several types of similarity relationships between languages, and for an arbitrary language class we define appropriate similarity classes. We show that for any of the classes of regular, linear, contextfree, context-sensitive, recursive and recursively enumerable languages the appropriate similarity classes form an uncountable hierarchy of order type ω + λ + 2. We also show that there exist linear languages which are not δ-similar to any regular language for any δ < 12 and we discuss this problem for δ ≥ 12 .
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