Dyck-based characterizations of Indexed Languages
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چکیده
Indexed languages are languages recognized by pushdown automata of level 2 and by indexed grammars. We propose here some new characterizations linking indexed languages to context-free languages: the class of indexed languages is the image of the Dyck language by a nice class of context-free transducers, it is also the class of images, by a projection defined by an FO-formula of nested words labelled by a Dyck word. This last result generalize the logical characterization of context-free languages.
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تاریخ انتشار 2014