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Two-Way Metalinear PC Grammar Systems and Their Descriptional Complexity
Alexander Meduna1
Acta Cybernetica 16 (2004) 385-397.
Abstract:
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,
, with two metalinear components in a very economical
way. Indeed, '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, makes a single communication step. Some variants of
two-way PC grammar systems are discussed in the conclusion of this paper.
Footnotes
... Meduna 1 Department of Information Systems, Faculty of Information Technology, Brno University of Technology, Bozetechova 2, Brno 61266, Czech Republic
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