A logical approach to fuzzy truth hedges

  • Authors:
  • Francesc Esteva;LluíS Godo;Carles Noguera

  • Affiliations:
  • Artificial Intelligence Research Institute (IIIA-CSIC), Campus de la Universitat Autònoma de Barcelona s/n, 08193 Bellaterra, Catalonia, Spain;Artificial Intelligence Research Institute (IIIA-CSIC), Campus de la Universitat Autònoma de Barcelona s/n, 08193 Bellaterra, Catalonia, Spain;Artificial Intelligence Research Institute (IIIA-CSIC), Campus de la Universitat Autònoma de Barcelona s/n, 08193 Bellaterra, Catalonia, Spain

  • Venue:
  • Information Sciences: an International Journal
  • Year:
  • 2013

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Abstract

The starting point of this paper are the works of Hajek and Vychodil on the axiomatization of truth-stressing and-depressing hedges as expansions of Hajek's BL logic by new unary connectives. They showed that their logics are chain-complete, but standard completeness was only proved for the expansions over Godel logic. We propose weaker axiomatizations over an arbitrary core fuzzy logic which have two main advantages: (i) they preserve the standard completeness properties of the original logic and (ii) any subdiagonal (resp. superdiagonal) non-decreasing function on [0,1] preserving 0 and 1 is a sound interpretation of the truth-stresser (resp. depresser) connectives. Hence, these logics accommodate most of the truth hedge functions used in the literature about of fuzzy logic in a broader sense.