YES We show the termination of the TRS R: app(id(),x) -> x app(plus(),|0|()) -> id() app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: app#(app(plus(),app(s(),x)),y) -> app#(s(),app(app(plus(),x),y)) p2: app#(app(plus(),app(s(),x)),y) -> app#(app(plus(),x),y) p3: app#(app(plus(),app(s(),x)),y) -> app#(plus(),x) and R consists of: r1: app(id(),x) -> x r2: app(plus(),|0|()) -> id() r3: app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) The estimated dependency graph contains the following SCCs: {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: app#(app(plus(),app(s(),x)),y) -> app#(app(plus(),x),y) and R consists of: r1: app(id(),x) -> x r2: app(plus(),|0|()) -> id() r3: app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) The set of usable rules consists of r2 Take the reduction pair: weighted path order base order: max/plus interpretations on natural numbers: app#_A(x1,x2) = max{1, x1 - 11} app_A(x1,x2) = max{x1 + 5, x2 + 5} plus_A = 0 s_A = 3 |0|_A = 3 id_A = 4 precedence: app# = app = s = |0| = id > plus partial status: pi(app#) = [] pi(app) = [1, 2] pi(plus) = [] pi(s) = [] pi(|0|) = [] pi(id) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.