Linear grammars with one-sided contexts and their automaton representation
Mikhail Barash, Alexander Okhotin
Abstract
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Mikhail Barash, Alexander Okhotin
Abstract
Open-access reader
The paper considers a family of formal grammars that extends linear context-free grammars with an operator for referring to the left context of a substring being defined, as well as with a conjunction operation (as in linear conjunctive grammars). These grammars are proved to be computationally equivalent to an extension of one-way real-time cellular automata with an extra data channel. The main result is the undecidability of the emptiness problem for grammars restricted to a one-symbol alphabet, which is proved by simulating a Turing machine by a cellular automaton with feedback. The same construction proves the Σ02-completeness of the finiteness problem for these grammars and automata.
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The paper considers a family of formal grammars that extends linear context-free grammars with an operator for referring to the left context of a substring being defined, as well as with a conjunction operation (as in linear conjunctive grammars). These grammars are proved to be computationally equivalent to an extension of one-way real-time cellular automata with an extra data channel. The main result is the undecidability of the emptiness problem for grammars restricted to a one-symbol alphabet, which is proved by simulating a Turing machine by a cellular automaton with feedback. The same construction proves the Σ02-completeness of the finiteness problem for these grammars and automata.
Key concepts: Embedded pushdown automaton, Tree-adjoining grammar, L-attributed grammar, Indexed grammar, Context-sensitive grammar, Deterministic context-free grammar, Phrase structure grammar, Context-free grammar