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: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: +#_A(x1,x2) = max{9, x1 + 6, x2 + 3} s_A(x1) = x1 + 3 +_A(x1,x2) = max{x1 + 3, x2 + 1} |0|_A = 2 precedence: +# = s > + = |0| partial status: pi(+#) = [1, 2] pi(s) = [1] pi(+) = [1, 2] pi(|0|) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: +#_A(x1,x2) = max{x1 + 2, x2} s_A(x1) = max{4, x1 + 2} +_A(x1,x2) = max{x1, x2 + 2} |0|_A = 1 precedence: +# = s = + = |0| partial status: pi(+#) = [2] pi(s) = [] pi(+) = [1] pi(|0|) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.