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Acta Informatica

, Volume 33, Issue 6, pp 571–593 | Cite as

The linear landscape of external contextual languages

  • Andrzej Ehrenfeucht
  • Gheorghe Păun
  • Grzegorz Rozenberg

Abstract.

The class of external contextual languages is strictly included in the class of linear languages. A reason for the strict inclusion in linear languages is that external contextual grammars generate languages in the exhaustive way: each sentential form belongs to the language of a grammar. In this paper we study the effect of adding various squeezing mechanisms to the basic classes of exhaustive contextual grammars. We obtain in this way a characterization of linear languages and a whole landscape of sublinear families. By restricting the contexts to be one-sided (only left-sided or only right-sided) we obtain a characterization of regular languages – here the subregular landscape reduces to two families.

Keywords

Basic Class Regular Language Strict Inclusion Sentential Form Contextual Grammar 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1996

Authors and Affiliations

  • Andrzej Ehrenfeucht
    • 1
  • Gheorghe Păun
    • 2
  • Grzegorz Rozenberg
    • 1
  1. 1.Department of Computer Science, University of Colorado at Boulder, Boulder, CO 80309, USAUS
  2. 2.Institute of Mathematics, Romanian Academy of Sciences, P.O. Box 1 – 764, RO-70700 Bucureşti, RomaniaRO

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