Dyck-based characterizations of Indexed Languages
arXiv:1409.6112
Abstract
Indexed languages are a generalization of context-free languages and form a proper subset of context-sensitive languages. We propose to generalize to indexed languages several well known characterizations of context-free languages: namely, the characterization by rational transductions defined by Nivat, the Chomsky-Schützenberger theorem, and the logical characterization proved by Lautemann et al.
The general approach can be improved and some statements are inaccurate