Počet záznamů: 1
On restricted context-free grammars
0367493 - MU-W 2012 RIV US eng J - Článek v odborném periodiku
Dassow, J. - Masopust, Tomáš
On restricted context-free grammars.
Journal of Computer and System Sciences. Roč. 78, č. 1 (2012), s. 293-304 ISSN 0022-0000
Výzkumný záměr: CEZ:AV0Z10190503
Klíčová slova: context-free grammars * derivation restriction * normal forms
Kód oboru RIV: BA - Obecná matematika
Impakt faktor: 1.000, rok: 2012
Context-free grammars are widely used for the simple form of their rules. A derivation step consists of the choice of a nonterminal of the sentential form and of an application of a rule rewriting it. Several regulations of the derivation process have been studied to increase the power of context-free grammars. In the resulting grammars, however, not only the symbols to be rewritten are restricted, but also the rules to be applied. In this paper, we study context-free grammars with a simpler restriction where only symbols to be rewritten are restricted, not the rules, in the sense that any rule rewriting the chosen nonterminal can be applied. We prove that these grammars have the same power as random context, matrix, or programmed grammars. We also present two improved normal forms and discuss the characterization of context-sensitive languages by a variant using strings of length at most two instead of symbols.
Trvalý link: http://hdl.handle.net/11104/0202154
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