Topic
Indexed language
About: Indexed language is a research topic. Over the lifetime, 334 publications have been published within this topic receiving 11000 citations.
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01 Aug 2000
2 citations
TL;DR: In this paper, a metatheorem for decision problems which can be represented by pairs of simple grammars was proved for the first time, showing that some relative decision problems concerning LR( k ), LL-regular, and LR-regular gramms and languages are undecidable.
2 citations
TL;DR: An extension for the concept of the finite index of context-free grammars is introduced and regular control languages are derived for the resulting family of languages generated by ordered Context-free Grammars.
Abstract: An extension for the concept of the finite index of context-free grammars is introduced and regular control languages are derived for the resulting family of languages generated by ordered context-free grammars.
2 citations
01 Jan 2014
TL;DR: It is shown that the full syntax of mainstream programming languages and of schema based XML documents cannot be modelled by either ET0L systems or indexed grammars.
Abstract: We revise and extend a couple of earlier incompletely published papers regarding the competence limits of formal systems in modelling the full syntax of programing languages. We show that the full syntax of mainstream programming languages (e.g. similar to Pascal or CAML) and of schema based XML documents cannot be modelled by either ET0L systems or indexed grammars. We raise a few open questions related to ET0L languages and two powerful but less known classes of languages: iterative languages and generalised Ogden-like languages.
2 citations
TL;DR: It is shown that if L is an indexed language, then α is a morphic word, i.e., α can be generated by iterating a morphism under a coding, and this implies that the infinite words determined by indexed languages are exactly the morphic words.
Abstract: We prove a pumping lemma in order to characterize the infinite words determined by indexed languages. An infinite language L determines an infinite word α if every string in L is a prefix of α. If L is regular or context-free, it is known that α must be ultimately periodic. We show that if L is an indexed language, then α is a morphic word, i.e., α can be generated by iterating a morphism under a coding. Since the other direction, that every morphic word is determined by some indexed language, also holds, this implies that the infinite words determined by indexed languages are exactly the morphic words. The pumping lemma which we use to obtain this result generalizes one recently proved for the class ET0L.
2 citations