On contra-symmetry and MPT conditionality in fuzzy logic

  • Authors:
  • E. Trillas;C. Alsina;E. Renedo;A. Pradera

  • Affiliations:
  • Departamento Inteligencia Artificial, Universidad Politécnica de Madrid, 28660, Boadilla del Monte, Madrid, Spain;Secció de Matemàtiques i Informàtica, Departament d'Estructures a l'Arquitectura, Universitat Politècnica de Catalunya, Diagonal, 649, 08028 Barcelona, Spain;Departamento Inteligencia Artificial, Universidad Politécnica de Madrid, 28660, Boadilla del Monte, Madrid, Spain;Departamento Informática, Estadística y Telemática, Universidad Rey Juan Carlos, Tulipán s/n, 28933 Móstoles, Madrid, Spain

  • Venue:
  • International Journal of Intelligent Systems
  • Year:
  • 2005

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Abstract

This article deals with the N-contrapositive symmetry of fuzzy implication operators J verifying either Modus Ponens or Modus Tollens inequalities, in a similar and complementary framework to the one in which Fodor (“Contrapositive symmetry of fuzzy implications.” Fuzzy Set Syst 1995;69:141–156) did begin with the subject in fuzzy logic, that is, with the verification of J(a, b) = J(N(b), N(a)) for all a, b in [0,1] and some strong-negation function N. This property corresponds to the classical p → q = ¬q → ¬p. The aim of this article is to study that property in relation to either Modus Ponens or Modus Tollens meta-rules of inference when the functions J are taken among those that belong to the usual families of implications in fuzzy logic. That is, the contra-positive of S implications, R implications, Q implications, and Mamdani–Larsen operators, verifying either Modus Ponens or Modus Tollens inequalities or both, the conditionality's aspect on which lies the complementarity with Fodor. Within this study new types of implication functions are introduced and analyzed. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 313–326, 2005.