YES(?,O(1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(1)). Strict Trs: { f(X) -> n__f(X) , f(f(a())) -> f(g(n__f(a()))) , activate(X) -> X , activate(n__f(X)) -> f(X) } Obligation: innermost runtime complexity Answer: YES(?,O(1)) Arguments of following rules are not normal-forms: { f(f(a())) -> f(g(n__f(a()))) } All above mentioned rules can be savely removed. We are left with following problem, upon which TcT provides the certificate YES(?,O(1)). Strict Trs: { f(X) -> n__f(X) , activate(X) -> X , activate(n__f(X)) -> f(X) } Obligation: innermost runtime complexity Answer: YES(?,O(1)) The input was oriented with the instance of 'Small Polynomial Path Order (PS,0-bounded)' as induced by the safe mapping safe(f) = {}, safe(a) = {}, safe(g) = {1}, safe(n__f) = {1}, safe(activate) = {} and precedence activate > f . Following symbols are considered recursive: {} The recursion depth is 0. For your convenience, here are the satisfied ordering constraints: f(X;) > n__f(; X) activate(X;) > X activate(n__f(; X);) > f(X;) Hurray, we answered YES(?,O(1))