YES proof: The input problem is infeasible because [1] the following set of Horn clauses is satisfiable: pos(p(x)) = false pos(s(x)) = true pos(0) = false pos(s(0)) = true pos(0) = true ==> true__ = false__ true__ = false__ ==> \bottom This holds because [2] the following E does not entail the following G (Claessen-Smallbone's transformation (2018)): E: pos(0) = false pos(p(x)) = false pos(s(0)) = true pos(s(x)) = true t1(pos(0)) = true__ t1(true) = false__ t2(false__) = true__ t2(true__) = false__ G: true__ = false__ This holds because [3] the following ground-complete ordered TRS entails E but does not entail G: false -> pos(0) pos(p(x)) -> pos(0) pos(s(x)) -> true t1(pos(0)) -> true__ t1(true) -> false__ t2(false__) -> true__ t2(true__) -> false__ with the LPO induced by t2 > t1 > p > false > 0 > s > true > pos > false__ > true__