On the Complexity of Validity Degrees in Łukasiewicz Logic
Abstrakt
Lukasiewicz logic is an established formal system of manyvalued logic. Decision problems in both propositional and first-order case have been classified as to their computational complexity or degrees of undecidability. For the propositional fragment, theoremhood and provability from finite theories are coNP complete. This paper extends the range of results by looking at validity degree in propositional Lukasiewicz logic, a natural optimization problem to find the minimal value of a term under a finite theory in a fixed complete semantics interpreting the logic. A classification for this problem is provided using the oracle class FPNP, where it is shown complete under metric reductions.