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2. On countermodels in basic logic
- Creator:
- Aguzzoli, Stefano and Gerla, Brunella
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- continuous t-norms, triangular logics, Basic Logic, and bounds on the cardinality of countermodels
- Language:
- English
- Description:
- In [3] the tautology problém for Hájek’s Basic Logic BL is proved to be co-NP-cornplete by showing that if a formula ϕ is not a tautology of BL then there exists an integer m > 0, polynomially bounded by the length of ϕ, such that ϕ fails to be a tautology in the infinite-valued logic mŁ corresponding to the ordinal sum of m copies of the Łukasiewicz t-norrn. In this paper we state that if ϕ is not a tautology of BL then it already fails to be a tautology of a finite set of finite-valued logics, defined by taking the ordinal sum of m copies of k-valued Łukasiewicz logics, for effectively determined integers m, k > 0 only depending on polynomial-time computable features of ϕ. This result allows the definition of a calculus for mŁ along the lines of [1], [2], while the analysis of the features of functions associated with formulas of mŁ constitutes a step toward the characterization of finitely generated free BL-algebras as algebras of [0, 1]-valued functions.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
3. Rational Łukasiewicz logic and DMV-algebras
- Creator:
- Gerla, Brunella
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- many-valued logic, fuzzy logic, Rational Łukasiewicz logic, DMV-algebras, completeness, and computational complexity
- Language:
- English
- Description:
- In this paper we present some results concerning the variety of divisible MV-algebras. Any free divisible MV-algebra is an algebra of continuous piecewise linear functions with rational coefficients. Correspondingly, the Rational Łukasiewicz logic is defined and its tautology problem is shown to be co-NP-complete.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public