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. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: f#_A(x1,x2) = ((0,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x1 + ((0,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x2 f_A(x1,x2) = ((1,0,0,0),(0,0,0,0),(0,0,0,0),(0,1,0,0)) x2 + (1,1,1,0) a_A() = (0,1,0,1) h_A(x1) = (0,1,1,1) 2. lexicographic path order with precedence: precedence: f > a > h > f# argument filter: 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. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: f#_A(x1,x2) = ((0,0,0,0),(1,0,0,0),(0,1,0,0),(1,1,1,0)) x2 f_A(x1,x2) = ((1,0,0,0),(1,1,0,0),(1,0,0,0),(0,1,1,0)) x2 + (1,1,1,0) a_A() = (1,1,1,1) h_A(x1) = (0,1,1,0) 2. lexicographic path order with precedence: precedence: f > a > h > f# argument filter: 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. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: f#_A(x1,x2) = ((0,0,0,0),(0,0,0,0),(1,0,0,0),(0,0,0,0)) x1 + ((1,0,0,0),(0,1,0,0),(0,1,1,0),(0,0,0,1)) x2 f_A(x1,x2) = ((0,0,0,0),(1,0,0,0),(0,1,0,0),(0,0,1,0)) x1 + ((1,0,0,0),(0,1,0,0),(0,1,0,0),(0,0,0,0)) x2 + (0,1,0,1) a_A() = (4,3,0,0) h_A(x1) = (0,1,1,1) 2. lexicographic path order with precedence: precedence: f# > f > a > h argument filter: 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.