YES We show the termination of the TRS R: f(x,f(a(),y)) -> f(a(),f(f(f(a(),x),h(a())),y)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,f(a(),y)) -> f#(a(),f(f(f(a(),x),h(a())),y)) p2: f#(x,f(a(),y)) -> f#(f(f(a(),x),h(a())),y) p3: f#(x,f(a(),y)) -> f#(f(a(),x),h(a())) p4: f#(x,f(a(),y)) -> f#(a(),x) and R consists of: r1: f(x,f(a(),y)) -> f(a(),f(f(f(a(),x),h(a())),y)) The estimated dependency graph contains the following SCCs: {p1, p2, p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,f(a(),y)) -> f#(a(),f(f(f(a(),x),h(a())),y)) p2: f#(x,f(a(),y)) -> f#(a(),x) p3: f#(x,f(a(),y)) -> f#(f(f(a(),x),h(a())),y) and R consists of: r1: f(x,f(a(),y)) -> f(a(),f(f(f(a(),x),h(a())),y)) The set of usable rules consists of r1 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: f#_A(x1,x2) = ((1,0),(1,0)) x1 + ((1,0),(1,0)) x2 + (3,2) f_A(x1,x2) = ((1,0),(1,0)) x2 + (2,0) a_A() = (0,1) h_A(x1) = (0,2) precedence: f# = f = a = h partial status: pi(f#) = [] pi(f) = [] pi(a) = [] pi(h) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: f#_A(x1,x2) = (0,0) f_A(x1,x2) = (1,1) a_A() = (2,2) h_A(x1) = (0,0) precedence: f# = f = a = h partial status: pi(f#) = [] pi(f) = [] pi(a) = [] pi(h) = [] The next rules are strictly ordered: p2 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,f(a(),y)) -> f#(a(),f(f(f(a(),x),h(a())),y)) p2: f#(x,f(a(),y)) -> f#(f(f(a(),x),h(a())),y) and R consists of: r1: f(x,f(a(),y)) -> f(a(),f(f(f(a(),x),h(a())),y)) The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,f(a(),y)) -> f#(a(),f(f(f(a(),x),h(a())),y)) p2: f#(x,f(a(),y)) -> f#(f(f(a(),x),h(a())),y) and R consists of: r1: f(x,f(a(),y)) -> f(a(),f(f(f(a(),x),h(a())),y)) The set of usable rules consists of r1 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1,x2) = max{x1 + 23, x2 + 83} f_A(x1,x2) = max{22, x2 + 15} a_A = 16 h_A(x1) = max{59, x1 + 41} precedence: f# = f > a > h partial status: pi(f#) = [] pi(f) = [] pi(a) = [] pi(h) = [1] 2. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1,x2) = 0 f_A(x1,x2) = 13 a_A = 10 h_A(x1) = max{25, x1 + 15} precedence: f# = f = a = h partial status: pi(f#) = [] pi(f) = [] pi(a) = [] pi(h) = [] The next rules are strictly ordered: p2 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,f(a(),y)) -> f#(a(),f(f(f(a(),x),h(a())),y)) and R consists of: r1: f(x,f(a(),y)) -> f(a(),f(f(f(a(),x),h(a())),y)) The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,f(a(),y)) -> f#(a(),f(f(f(a(),x),h(a())),y)) and R consists of: r1: f(x,f(a(),y)) -> f(a(),f(f(f(a(),x),h(a())),y)) The set of usable rules consists of r1 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: f#_A(x1,x2) = x2 + (1,3) f_A(x1,x2) = ((0,1),(0,0)) x1 + ((1,0),(0,0)) x2 + (5,0) a_A() = (4,2) h_A(x1) = ((1,0),(0,0)) x1 + (0,3) precedence: f# = f = a = h partial status: pi(f#) = [] pi(f) = [] pi(a) = [] pi(h) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: f#_A(x1,x2) = ((1,1),(0,0)) x2 + (1,2) f_A(x1,x2) = (2,1) a_A() = (2,1) h_A(x1) = (1,0) precedence: a > f > f# = h partial status: pi(f#) = [] pi(f) = [] pi(a) = [] pi(h) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.