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Acta Informatica

, Volume 33, Issue 5, pp 571–593 | Cite as

The linear landscape of external contextual languages

  • Andrzej Ehrenfeucht
  • Gheorghe Păun
  • Grzegorz Rozenberg
Article

Abstract

The class of external contextual languages isstrictly 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

Regular Language Contextual Grammar Enumerable Language Finite Language Alphabet Versus 
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 1996

Authors and Affiliations

  • Andrzej Ehrenfeucht
    • 1
  • Gheorghe Păun
    • 2
  • Grzegorz Rozenberg
    • 3
    • 4
  1. 1.Department of Computer ScienceUniversity of Colorado at BoulderBoulderUSA
  2. 2.Institute of MathematicsRomanian Academy of SciencesBucureştiRomania
  3. 3.Department of Computer ScienceLeiden UniversityLeidenThe Netherlands
  4. 4.Department of Computer ScienceUniversity of Colorado at BoulderBoulderUSA

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