Formal languages
Acta Cybernetica
On cooperating/distributed grammar systems
Journal of Information Processing and Cybernetics
Petri net algorithms in the theory of matrix grammars
Acta Informatica
Handbook of formal languages, vol. 2
A shrinking lemma for random forbidding context languages
Theoretical Computer Science
A pumping lemma for random permitting context languages
Theoretical Computer Science
Context-Free-Like Forms for the Phrase-Structure Grammars
MFCS '88 Proceedings of the Mathematical Foundations of Computer Science 1988
An hierarchy between context-free and context-sensitive languages
Journal of Computer and System Sciences
| Hi-index | 5.23 |
A left-forbidding grammar, introduced in this paper, is a context-free grammar, where a set of nonterminal symbols is attached to each context-free production. Such a production can rewrite a nonterminal provided that no symbol from the attached set occurs to the left of the rewritten nonterminal in the current sentential form. The present paper discusses cooperating distributed grammar systems with left-forbidding grammars as components and gives some new characterizations of language families of the Chomsky hierarchy. In addition, it also proves that twelve nonterminals are enough for cooperating distributed grammar systems working in the terminal derivation mode with two left-forbidding components (including erasing productions) to characterize the family of recursively enumerable languages.