Journal of Logic and Computation Advance Access originally published online on June 27, 2008
Journal of Logic and Computation 2008 18(6):941-958; doi:10.1093/logcom/exn017
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Original Articles |
On Computational Complexity of Semilinear Varieties
Department of Information and Communication Sciences, Open University of Catalonia, Rambla del Poblenou 156, 08018 Barcelona, Spain.
E-mail: enrico{at}iiia.csic.es
Received 30 March 2007.
| Abstract |
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We propose a method for characterizing the complexity of satisfiability and tautologicity of equational theories of varieties of algebras by relying on their representability in the theory of the ordered additive group of reals 
with rational constants. We call semilinear those varieties which are generated by a subclass of algebras in which the operations are representable as semilinear functions with rational coefficients. Those functions are definable in the theory of 
which admits quantifier elimination and whose existential theory is NP-complete. We prove that there is a polynomial time translation of the equational theories of semilinear varieties into the existential theory of 
. Then, if the variety is generated (up to isomorphism) by one semilinear algebra, the satisfiability problem is in NP, while the tautologicity problem is in co-NP. We apply this method in order to provide a comprehensive study of complexity of several varieties related to logics based on left-continuous conjunctive uninorms and left-continuous t-norms.
Keywords: Computational complexity; ordered divisible Abelian groups; varieties; semilinear functions; uninorms; triangular norms