YES(?,POLY) We are left with following problem, upon which TcT provides the certificate YES(?,POLY). Strict Trs: { a__f(X) -> g(h(f(X))) , a__f(X) -> f(X) , mark(g(X)) -> g(X) , mark(h(X)) -> h(mark(X)) , mark(f(X)) -> a__f(mark(X)) } Obligation: innermost runtime complexity Answer: YES(?,POLY) The input was oriented with the instance of 'Polynomial Path Order' as induced by the safe mapping safe(a__f) = {1}, safe(g) = {1}, safe(h) = {1}, safe(f) = {1}, safe(mark) = {} and precedence mark > a__f . Following symbols are considered recursive: {a__f, mark} The recursion depth is 2. For your convenience, here are the satisfied ordering constraints: a__f(; X) > g(; h(; f(; X))) a__f(; X) > f(; X) mark(g(; X);) > g(; X) mark(h(; X);) > h(; mark(X;)) mark(f(; X);) > a__f(; mark(X;)) Hurray, we answered YES(?,POLY)