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: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: app#_A(x1,x2) = ((0,0),(1,0)) x1 + (1,1) app_A(x1,x2) = ((1,0),(0,0)) x2 + (3,8) plus_A() = (4,10) s_A() = (2,9) |0|_A() = (1,12) id_A() = (0,11) precedence: plus = s > |0| > app# = app = id partial status: pi(app#) = [] pi(app) = [] pi(plus) = [] pi(s) = [] pi(|0|) = [] pi(id) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: app#_A(x1,x2) = (0,0) app_A(x1,x2) = (3,3) plus_A() = (1,1) s_A() = (2,2) |0|_A() = (3,3) id_A() = (2,2) precedence: id > plus > |0| > app > app# = s partial status: pi(app#) = [] pi(app) = [] 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.