YES We show the termination of the TRS R: +(|0|(),y) -> y +(s(x),|0|()) -> s(x) +(s(x),s(y)) -> s(+(s(x),+(y,|0|()))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: +#(s(x),s(y)) -> +#(s(x),+(y,|0|())) p2: +#(s(x),s(y)) -> +#(y,|0|()) and R consists of: r1: +(|0|(),y) -> y r2: +(s(x),|0|()) -> s(x) r3: +(s(x),s(y)) -> s(+(s(x),+(y,|0|()))) The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: +#(s(x),s(y)) -> +#(s(x),+(y,|0|())) and R consists of: r1: +(|0|(),y) -> y r2: +(s(x),|0|()) -> s(x) r3: +(s(x),s(y)) -> s(+(s(x),+(y,|0|()))) The set of usable rules consists of r1, r2 Take the reduction pair: weighted path order base order: matrix interpretations: carrier: N^2 order: standard order interpretations: +#_A(x1,x2) = ((1,1),(1,1)) x1 + ((1,1),(1,1)) x2 + (1,0) s_A(x1) = ((1,1),(1,1)) x1 + (1,3) +_A(x1,x2) = ((1,1),(1,1)) x1 + x2 |0|_A() = (2,1) precedence: +# = s = + = |0| partial status: pi(+#) = [] pi(s) = [] pi(+) = [2] pi(|0|) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.