Formal languages
On the power of cooperation: a regular representation of recursively enumerable languages
Theoretical Computer Science
Handbook of formal languages, vol. 2
On simulating non-returning PC grammar systems with returning systems
Theoretical Computer Science
Automata and languages: theory and applications
Automata and languages: theory and applications
Grammar Systems: A Grammatical Approach to Distribution and Cooperation
Grammar Systems: A Grammatical Approach to Distribution and Cooperation
Cooperating Grammars' Systems: Power and Parameters
Proceedings of the Colloquium in Honor of Arto Salomaa on Results and Trends in Theoretical Computer Science
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Besides a derivation step and a communication step, a two-way PC grammar system can make a reduction step during which it reduces the right-hand side of a context-free production to its left hand-side. This paper proves that every non-unary recursively enumerable language is defined by a centralized two-way grammar system, Γ, with two metalinear components in a very economical way. Indeed, Γ's master has only three nonterminals and one communication production; furthermore, it produces all sentential forms with no more than two occurrences of nonterminals. In addition, during every computation, Γ makes a single communication step. Some variants of two-way PC grammar systems are discussed in the conclusion of this paper.