YES Problem: a(b(x1)) -> b(a(a(x1))) b(x1) -> c(a(c(x1))) a(a(x1)) -> a(c(a(x1))) Proof: Matrix Interpretation Processor: dim=1 interpretation: [a](x0) = x0, [b](x0) = x0 + 4, [c](x0) = x0 orientation: a(b(x1)) = x1 + 4 >= x1 + 4 = b(a(a(x1))) b(x1) = x1 + 4 >= x1 = c(a(c(x1))) a(a(x1)) = x1 >= x1 = a(c(a(x1))) problem: a(b(x1)) -> b(a(a(x1))) a(a(x1)) -> a(c(a(x1))) Matrix Interpretation Processor: dim=3 interpretation: [1 1 0] [a](x0) = [0 0 1]x0 [0 1 0] , [1 0 0] [0] [b](x0) = [0 1 1]x0 + [1] [0 1 1] [1], [1 0 0] [c](x0) = [0 0 0]x0 [0 0 0] orientation: [1 1 1] [1] [1 1 1] [0] a(b(x1)) = [0 1 1]x1 + [1] >= [0 1 1]x1 + [1] = b(a(a(x1))) [0 1 1] [1] [0 1 1] [1] [1 1 1] [1 1 0] a(a(x1)) = [0 1 0]x1 >= [0 0 0]x1 = a(c(a(x1))) [0 0 1] [0 0 0] problem: a(a(x1)) -> a(c(a(x1))) Bounds Processor: bound: 2 enrichment: match automaton: final states: {3} transitions: c1(9) -> 10* c1(12) -> 13* c2(21) -> 22* a2(20) -> 21* a2(22) -> 23* a0(3) -> 3* a1(10) -> 11* a1(8) -> 9* c0(3) -> 3* 11 -> 9,12,3 13 -> 10* 3 -> 8* 10 -> 20* 23 -> 9* problem: Qed