YES We show the termination of the TRS R: f(s(x),y) -> f(x,s(x)) f(x,s(y)) -> f(y,x) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(x)) p2: f#(x,s(y)) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) 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#(s(x),y) -> f#(x,s(x)) p2: f#(x,s(y)) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: f#_A(x1,x2) = ((1,1),(0,0)) x1 + ((0,1),(0,0)) x2 + (1,2) s_A(x1) = ((1,1),(1,1)) x1 + (3,1) precedence: f# = s partial status: pi(f#) = [] pi(s) = [1] The next rules are strictly ordered: p1 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,s(y)) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) 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,s(y)) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) The set of usable rules consists of (no rules) Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: f#_A(x1,x2) = ((1,1),(1,1)) x1 + ((1,1),(1,0)) x2 + (2,2) s_A(x1) = ((1,1),(0,0)) x1 + (1,1) precedence: s > f# partial status: pi(f#) = [1] pi(s) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.