YES We show the termination of the TRS R: f(f(X)) -> c(n__f(g(n__f(X)))) c(X) -> d(activate(X)) h(X) -> c(n__d(X)) f(X) -> n__f(X) d(X) -> n__d(X) activate(n__f(X)) -> f(X) activate(n__d(X)) -> d(X) activate(X) -> X -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(f(X)) -> c#(n__f(g(n__f(X)))) p2: c#(X) -> d#(activate(X)) p3: c#(X) -> activate#(X) p4: h#(X) -> c#(n__d(X)) p5: activate#(n__f(X)) -> f#(X) p6: activate#(n__d(X)) -> d#(X) and R consists of: r1: f(f(X)) -> c(n__f(g(n__f(X)))) r2: c(X) -> d(activate(X)) r3: h(X) -> c(n__d(X)) r4: f(X) -> n__f(X) r5: d(X) -> n__d(X) r6: activate(n__f(X)) -> f(X) r7: activate(n__d(X)) -> d(X) r8: activate(X) -> X The estimated dependency graph contains the following SCCs: {p1, p3, p5} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(f(X)) -> c#(n__f(g(n__f(X)))) p2: c#(X) -> activate#(X) p3: activate#(n__f(X)) -> f#(X) and R consists of: r1: f(f(X)) -> c(n__f(g(n__f(X)))) r2: c(X) -> d(activate(X)) r3: h(X) -> c(n__d(X)) r4: f(X) -> n__f(X) r5: d(X) -> n__d(X) r6: activate(n__f(X)) -> f(X) r7: activate(n__d(X)) -> d(X) r8: activate(X) -> X The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1) = max{4, x1} f_A(x1) = max{12, x1 + 11} c#_A(x1) = x1 + 3 n__f_A(x1) = max{6, x1 + 2} g_A(x1) = 0 activate#_A(x1) = max{3, x1 + 1} precedence: f# = f = c# = n__f = activate# > g partial status: pi(f#) = [1] pi(f) = [1] pi(c#) = [1] pi(n__f) = [1] pi(g) = [] pi(activate#) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1) = x1 + 20 f_A(x1) = max{12, x1 + 8} c#_A(x1) = max{13, x1 + 12} n__f_A(x1) = x1 + 9 g_A(x1) = 2 activate#_A(x1) = x1 + 11 precedence: f# = f = c# = n__f = g = activate# partial status: pi(f#) = [1] pi(f) = [1] pi(c#) = [1] pi(n__f) = [1] pi(g) = [] pi(activate#) = [1] The next rules are strictly ordered: p1, p2, p3 We remove them from the problem. Then no dependency pair remains.