Abstract
In this paper we consider the expansions of logics of a left-continuous t-norm with truth-constants from a subalgebra of the rational unit interval. From known results on standard semantics, we study completeness for these propositional logics with respect to chains defined over the rational unit interval with a special attention to the completeness with respect to the canonical chain, i.e. the algebra over \([0,1] \cap {{\mathbb{Q}}}\) where each truth-constant is interpreted in its corresponding rational truth-value. Finally, we study rational completeness results when we restrict ourselves to deductions between the so-called evaluated formulae.
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Notes
See Běhounek and Cintula (2006) for some rationale supporting the idea of fuzzy logics as the logics of chains.
Notice that we could consider parameterized isomorphic t-norms \(*^c_{n_1}\) or \(*^c_{n_2}\) : in the first the case by defining the negation using any \(c \in (0,1)\) instead of \({\frac{1}{2}},\) and in the second case by using any \(c \in ({\frac{1}{2}},1)\) instead of \({\frac{2}{3}}\) (and \(1-c\) instead of \({\frac{1}{3}}\)).
Looking at Table 2, this is the case of the S\({\fancyscript{R}}\)C and the Canonical completeness properties for some of the logics under our scope.
Notice that the particular choice of an element \(a \in (0,1)^{\mathbb{Q}}\) is not important, as all the resulting algebras are isomorphic and hence they yield the same logic.
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Acknowledgments
The authors acknowledge partial support by the Spanish project MULOG2 (TIN2007-68005-C04), including feder funds of the European Union, and by the Generalitat de Catalunya grant 2005-SGR-00093. The third author also acknowledges partial support from the grant 2006-BP-A-10043 of the Departament d’Educació i Universitats of the Generalitat de Catalunya.
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This is an extended and revised version of the paper Rational Completeness Results for Prominent Propositional Fuzzy Logics with Truth-Constants. Proc. of ESTYLF’08, Mieres, Spain, pp. 133–139.
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Esteva, F., Godo, L. & Noguera, C. Expanding the propositional logic of a t-norm with truth-constants: completeness results for rational semantics. Soft Comput 14, 273–284 (2010). https://doi.org/10.1007/s00500-009-0402-8
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DOI: https://doi.org/10.1007/s00500-009-0402-8