YES We show the termination of the TRS R: a(b(x)) -> b(a(a(x))) b(c(x)) -> c(b(b(x))) c(a(x)) -> a(c(c(x))) u(a(x)) -> x v(b(x)) -> x w(c(x)) -> x a(u(x)) -> x b(v(x)) -> x c(w(x)) -> x -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: a#(b(x)) -> b#(a(a(x))) p2: a#(b(x)) -> a#(a(x)) p3: a#(b(x)) -> a#(x) p4: b#(c(x)) -> c#(b(b(x))) p5: b#(c(x)) -> b#(b(x)) p6: b#(c(x)) -> b#(x) p7: c#(a(x)) -> a#(c(c(x))) p8: c#(a(x)) -> c#(c(x)) p9: c#(a(x)) -> c#(x) and R consists of: r1: a(b(x)) -> b(a(a(x))) r2: b(c(x)) -> c(b(b(x))) r3: c(a(x)) -> a(c(c(x))) r4: u(a(x)) -> x r5: v(b(x)) -> x r6: w(c(x)) -> x r7: a(u(x)) -> x r8: b(v(x)) -> x r9: c(w(x)) -> x The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4, p5, p6, p7, p8, p9} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: a#(b(x)) -> b#(a(a(x))) p2: b#(c(x)) -> b#(x) p3: b#(c(x)) -> b#(b(x)) p4: b#(c(x)) -> c#(b(b(x))) p5: c#(a(x)) -> c#(x) p6: c#(a(x)) -> c#(c(x)) p7: c#(a(x)) -> a#(c(c(x))) p8: a#(b(x)) -> a#(x) p9: a#(b(x)) -> a#(a(x)) and R consists of: r1: a(b(x)) -> b(a(a(x))) r2: b(c(x)) -> c(b(b(x))) r3: c(a(x)) -> a(c(c(x))) r4: u(a(x)) -> x r5: v(b(x)) -> x r6: w(c(x)) -> x r7: a(u(x)) -> x r8: b(v(x)) -> x r9: c(w(x)) -> x The set of usable rules consists of r1, r2, r3, r7, r8, r9 Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^1 order: standard order interpretations: a#_A(x1) = x1 b_A(x1) = x1 b#_A(x1) = x1 a_A(x1) = x1 c_A(x1) = x1 c#_A(x1) = x1 u_A(x1) = x1 + 1 v_A(x1) = x1 + 1 w_A(x1) = x1 + 1 2. matrix interpretations: carrier: N^1 order: standard order interpretations: a#_A(x1) = 2 b_A(x1) = x1 b#_A(x1) = x1 a_A(x1) = 1 c_A(x1) = x1 + 4 c#_A(x1) = 3 u_A(x1) = 0 v_A(x1) = 1 w_A(x1) = 0 The next rules are strictly ordered: p1, p2, p3, p4, p7 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: c#(a(x)) -> c#(x) p2: c#(a(x)) -> c#(c(x)) p3: a#(b(x)) -> a#(x) p4: a#(b(x)) -> a#(a(x)) and R consists of: r1: a(b(x)) -> b(a(a(x))) r2: b(c(x)) -> c(b(b(x))) r3: c(a(x)) -> a(c(c(x))) r4: u(a(x)) -> x r5: v(b(x)) -> x r6: w(c(x)) -> x r7: a(u(x)) -> x r8: b(v(x)) -> x r9: c(w(x)) -> x The estimated dependency graph contains the following SCCs: {p1, p2} {p3, p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: c#(a(x)) -> c#(x) p2: c#(a(x)) -> c#(c(x)) and R consists of: r1: a(b(x)) -> b(a(a(x))) r2: b(c(x)) -> c(b(b(x))) r3: c(a(x)) -> a(c(c(x))) r4: u(a(x)) -> x r5: v(b(x)) -> x r6: w(c(x)) -> x r7: a(u(x)) -> x r8: b(v(x)) -> x r9: c(w(x)) -> x The set of usable rules consists of r1, r2, r3, r7, r8, r9 Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^1 order: standard order interpretations: c#_A(x1) = x1 a_A(x1) = x1 c_A(x1) = x1 b_A(x1) = x1 v_A(x1) = x1 + 1 u_A(x1) = x1 + 1 w_A(x1) = x1 + 1 2. matrix interpretations: carrier: N^1 order: standard order interpretations: c#_A(x1) = x1 a_A(x1) = x1 + 1 c_A(x1) = x1 b_A(x1) = 1 v_A(x1) = 0 u_A(x1) = 0 w_A(x1) = 1 The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: a#(b(x)) -> a#(x) p2: a#(b(x)) -> a#(a(x)) and R consists of: r1: a(b(x)) -> b(a(a(x))) r2: b(c(x)) -> c(b(b(x))) r3: c(a(x)) -> a(c(c(x))) r4: u(a(x)) -> x r5: v(b(x)) -> x r6: w(c(x)) -> x r7: a(u(x)) -> x r8: b(v(x)) -> x r9: c(w(x)) -> x The set of usable rules consists of r1, r2, r3, r7, r8, r9 Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^1 order: standard order interpretations: a#_A(x1) = x1 b_A(x1) = x1 a_A(x1) = x1 c_A(x1) = x1 w_A(x1) = x1 + 1 v_A(x1) = x1 + 1 u_A(x1) = x1 + 1 2. matrix interpretations: carrier: N^1 order: standard order interpretations: a#_A(x1) = x1 b_A(x1) = x1 + 1 a_A(x1) = x1 c_A(x1) = 1 w_A(x1) = 0 v_A(x1) = 0 u_A(x1) = 1 The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.