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