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. lexicographic path order with precedence: precedence: w > u > a > c# > a# > b# > c > v > b argument filter: pi(a#) = 1 pi(b) = 1 pi(b#) = 1 pi(a) = 1 pi(c) = 1 pi(c#) = 1 pi(u) = 1 pi(v) = [1] pi(w) = 1 2. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: a#_A(x1) = (3,0,15,7) b_A(x1) = ((0,0,0,0),(1,0,0,0),(0,0,0,0),(0,0,0,0)) x1 + (1,3,7,0) b#_A(x1) = (2,6,8,6) a_A(x1) = ((1,0,0,0),(0,0,0,0),(1,0,0,0),(1,0,0,0)) x1 + (7,1,7,8) c_A(x1) = ((1,0,0,0),(0,0,0,0),(1,1,0,0),(1,0,0,0)) x1 + (0,2,1,0) c#_A(x1) = ((1,0,0,0),(1,1,0,0),(1,0,1,0),(1,1,0,0)) x1 u_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(0,0,0,0)) x1 + (1,1,1,1) v_A(x1) = ((0,0,0,0),(1,0,0,0),(1,1,0,0),(0,0,0,0)) x1 + (1,1,1,1) w_A(x1) = ((1,0,0,0),(1,1,0,0),(1,1,1,0),(1,1,1,0)) x1 + (1,1,0,0) The next rules are strictly ordered: p1, p4, p5, p6, p7 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: b#(c(x)) -> b#(x) p2: b#(c(x)) -> b#(b(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: b#(c(x)) -> b#(x) p2: b#(c(x)) -> b#(b(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. lexicographic path order with precedence: precedence: v > w > a > b# > u > c > b argument filter: pi(b#) = [1] pi(c) = 1 pi(b) = 1 pi(a) = 1 pi(u) = [1] pi(w) = 1 pi(v) = 1 2. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: b#_A(x1) = ((1,0,0,0),(0,1,0,0),(0,1,0,0),(0,1,0,0)) x1 c_A(x1) = x1 + (0,2,1,1) b_A(x1) = ((1,0,0,0),(0,1,0,0),(0,0,0,0),(0,1,0,0)) x1 + (0,0,2,0) a_A(x1) = (1,3,3,2) u_A(x1) = x1 + (1,1,1,0) w_A(x1) = x1 + (1,1,1,0) v_A(x1) = ((1,0,0,0),(0,1,0,0),(1,1,0,0),(0,0,0,0)) x1 + (1,1,1,0) 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. lexicographic path order with precedence: precedence: w > b > u > v > c > a# > a argument filter: pi(a#) = [1] pi(b) = 1 pi(a) = 1 pi(c) = 1 pi(w) = [1] pi(v) = 1 pi(u) = 1 2. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: a#_A(x1) = ((1,0,0,0),(1,0,0,0),(0,0,0,0),(1,0,0,0)) x1 b_A(x1) = ((1,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x1 + (2,1,1,2) a_A(x1) = ((1,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x1 + (0,1,1,1) c_A(x1) = (1,1,1,2) w_A(x1) = (1,1,0,0) v_A(x1) = x1 + (1,1,1,0) u_A(x1) = x1 + (1,1,1,0) The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.