YES Problem: f(c(a(),z,x)) -> b(a(),z) b(x,b(z,y)) -> f(b(f(f(z)),c(x,z,y))) b(y,z) -> z Proof: Matrix Interpretation Processor: dim=1 interpretation: [b](x0, x1) = 4x0 + 2x1 + 4, [f](x0) = x0, [c](x0, x1, x2) = x0 + 2x1 + x2 + 4, [a] = 0 orientation: f(c(a(),z,x)) = x + 2z + 4 >= 2z + 4 = b(a(),z) b(x,b(z,y)) = 4x + 4y + 8z + 12 >= 2x + 2y + 8z + 12 = f(b(f(f(z)),c(x,z,y))) b(y,z) = 4y + 2z + 4 >= z = z problem: f(c(a(),z,x)) -> b(a(),z) b(x,b(z,y)) -> f(b(f(f(z)),c(x,z,y))) Matrix Interpretation Processor: dim=2 interpretation: [2 0] [2 2] [0] [b](x0, x1) = [1 2]x0 + [0 0]x1 + [2], [1 0] [0] [f](x0) = [0 0]x0 + [2], [1 0] [2 2] [1 2] [1] [c](x0, x1, x2) = [0 0]x0 + [0 0]x1 + [1 0]x2 + [1], [0] [a] = [0] orientation: [1 2] [2 2] [1] [2 2] [0] f(c(a(),z,x)) = [0 0]x + [0 0]z + [2] >= [0 0]z + [2] = b(a(),z) [2 0] [4 4] [6 4] [4] [2 0] [4 4] [6 4] [4] b(x,b(z,y)) = [1 2]x + [0 0]y + [0 0]z + [2] >= [0 0]x + [0 0]y + [0 0]z + [2] = f(b(f(f(z)),c(x,z,y))) problem: b(x,b(z,y)) -> f(b(f(f(z)),c(x,z,y))) Matrix Interpretation Processor: dim=1 interpretation: [b](x0, x1) = 2x0 + 2x1 + 5, [f](x0) = x0 + 1, [c](x0, x1, x2) = x0 + x1 + 2x2 orientation: b(x,b(z,y)) = 2x + 4y + 4z + 15 >= 2x + 4y + 4z + 10 = f(b(f(f(z)),c(x,z,y))) problem: Qed