一句话:证明三守卫片段具有有限模型性质,并确定其及相关带传递守卫片段的有限可满足性复杂度。
本文研究一阶逻辑中表达能力很强的可判定片段——三守卫片段(TGF)的有限模型论。TGF 可包含无等词的双变量片段和守卫片段。作者证明 TGF 具有有限模型性质,并给出模型大小的紧致双指数上界;由此,TGF 的有限可满足性与可满足性一致,而后者已知为 N2ExpTime 完全。作者采用类似构造,进一步证明无常量(三)守卫片段在带传递守卫时的有限可满足性是 2ExpTime 完全的。这些结果厘清了有限模型语义下相关逻辑的判定复杂度与模型规模界限。
The Triguarded Fragment (TGF) is among the most expressive decidable fragments of first-order logic, subsuming both its two-variable and guarded fragments without equality. We show that the TGF has the finite model property (providing a tight doubly exponential bound on the model size) and hence finite satisfiability coincides with satisfiability known to be N2ExpTime-complete. Using similar constructions, we also establish 2ExpTime-completeness for finite satisfiability of the constant-free (tri)guarded fragment with transitive guards.