Factorizations of languages and commutativity conditions

  • Authors:
  • Alexandru Mateescu;Arto Salomaa;Sheng Yu

  • Affiliations:
  • Faculty of Mathematics, University of Bucharest Academiei, 14, Bucharest, Romania;Turku Centre for Computer Science (TUCS) Lemminkäisenkatu 14A, 20520 Turku, Finland;Department of Computer Science, University of Western Ontario London, Ontario, Canada N6A 5B7

  • Venue:
  • Acta Cybernetica
  • Year:
  • 2002

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Abstract

Representations of languages as a product (catenation) of languages are investigated, where the factor languages are "prime", that is, cannot be decomposed further in a nontrivial manner. In general, such prime decompositions do not necessarily exist. If they exist, they are not necessarily unique - the number of factors can vary even exponentially. The paper investigates prime decompositions, as well as the commuting of the factors, especially for the case of finite languages. In particular, a technique about commuting is developed in Section 4, where the factorization of languages L1 and L2 is discussed under the assumption L1L2 = L2L1.