YES Problem: d(a(x1)) -> b(d(x1)) b(x1) -> a(a(a(x1))) c(d(c(x1))) -> a(d(x1)) b(d(d(x1))) -> c(c(d(d(c(x1))))) Proof: Matrix Interpretation Processor: dim=1 interpretation: [c](x0) = x0 + 1, [b](x0) = x0 + 12, [d](x0) = 3x0, [a](x0) = x0 + 4 orientation: d(a(x1)) = 3x1 + 12 >= 3x1 + 12 = b(d(x1)) b(x1) = x1 + 12 >= x1 + 12 = a(a(a(x1))) c(d(c(x1))) = 3x1 + 4 >= 3x1 + 4 = a(d(x1)) b(d(d(x1))) = 9x1 + 12 >= 9x1 + 11 = c(c(d(d(c(x1))))) problem: d(a(x1)) -> b(d(x1)) b(x1) -> a(a(a(x1))) c(d(c(x1))) -> a(d(x1)) Arctic Interpretation Processor: dimension: 2 interpretation: [0 0] [c](x0) = [2 2]x0, [0 0 ] [b](x0) = [-& 3 ]x0, [0 3 ] [d](x0) = [-& -&]x0, [0 -&] [a](x0) = [-& 1 ]x0 orientation: [0 4 ] [0 3 ] d(a(x1)) = [-& -&]x1 >= [-& -&]x1 = b(d(x1)) [0 0 ] [0 -&] b(x1) = [-& 3 ]x1 >= [-& 3 ]x1 = a(a(a(x1))) [5 5] [0 3 ] c(d(c(x1))) = [7 7]x1 >= [-& -&]x1 = a(d(x1)) problem: d(a(x1)) -> b(d(x1)) b(x1) -> a(a(a(x1))) Bounds Processor: bound: 1 enrichment: match automaton: final states: {4,1} transitions: a0(5) -> 6* a0(2) -> 5* a0(6) -> 4* a1(7) -> 8* a1(9) -> 10* a1(8) -> 9* f40() -> 2* b0(3) -> 1* d0(2) -> 3* 1 -> 3,7 3 -> 7* 10 -> 1* problem: Qed