fact: Definition fo_model_dec Σ X (M : fo_model Σ X) := forall r (v : vec _ (ar_rels _ r)), { fom_rels M r v } + { ~ fom_rels M r v }.
imports: List Arith Lia Undecidability.Shared.Libs.DLW.Vec(pos vec) Undecidability.FOL.TRAKHTENBROT(notations)