YES proof: The input problem is infeasible because [1] the following set of Horn clauses is satisfiable: x = c ==> g(x) = c x = a ==> f(g(x)) = b x = a & x = c ==> true__ = false__ true__ = false__ ==> \bottom This holds because [2] the following E does not entail the following G (Claessen-Smallbone's transformation (2018)): E: f(g(a)) = b g(c) = c t1(a) = true__ t1(c) = 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: b -> f(g(a)) g(c) -> c t1(a) -> true__ t1(c) -> false__ t2(false__) -> true__ t2(true__) -> false__ with the LPO induced by t2 > b > g > a > c > f > t1 > false__ > true__