YES Problem: a(a(a(a(x1)))) -> b(b(x1)) b(b(a(a(x1)))) -> a(a(b(b(x1)))) b(b(b(b(c(c(x1)))))) -> c(c(a(a(x1)))) b(b(b(b(x1)))) -> a(a(a(a(a(a(x1)))))) c(c(a(a(x1)))) -> b(b(a(a(c(c(x1)))))) Proof: Matrix Interpretation Processor: dim=1 interpretation: [b](x0) = x0 + 2, [a](x0) = x0 + 1, [c](x0) = 2x0 orientation: a(a(a(a(x1)))) = x1 + 4 >= x1 + 4 = b(b(x1)) b(b(a(a(x1)))) = x1 + 6 >= x1 + 6 = a(a(b(b(x1)))) b(b(b(b(c(c(x1)))))) = 4x1 + 8 >= 4x1 + 8 = c(c(a(a(x1)))) b(b(b(b(x1)))) = x1 + 8 >= x1 + 6 = a(a(a(a(a(a(x1)))))) c(c(a(a(x1)))) = 4x1 + 8 >= 4x1 + 6 = b(b(a(a(c(c(x1)))))) problem: a(a(a(a(x1)))) -> b(b(x1)) b(b(a(a(x1)))) -> a(a(b(b(x1)))) b(b(b(b(c(c(x1)))))) -> c(c(a(a(x1)))) KBO Processor: weight function: w0 = 1 w(b) = w(a) = 1 w(c) = 0 precedence: c > b > a problem: Qed