Skolemization and Decidability of the Bernays-Schoenfinkel Class in Goedel Logics

Abstract

In 1928, Bernays and Schoenfinkel proved the decidability of prenex sentences whose matrices contain no function symbols, now known as the Bernays-Schoenfinkel (BS) class. We investigate the decidability of the BS class for all Goedel logics. Our validity argument relies on the fact that Skolemization works for prenex Goedel logics, while 1-satisfiability follows from structural properties of prenex formulas. We show that validity and 1-satisfiability for the BS class are decidable in every Goedel logic, and that these properties persist across all infinite Goedel logics.