YES Problem: a(b(b(a(x1)))) -> a(c(a(b(x1)))) a(c(x1)) -> c(c(a(x1))) c(c(c(x1))) -> b(c(b(x1))) Proof: Matrix Interpretation Processor: dim=3 interpretation: [1 0 0] [b](x0) = [0 1 0]x0 [0 1 0] , [1 0 1] [0] [a](x0) = [0 1 0]x0 + [1] [0 0 0] [0], [1 0 0] [c](x0) = [0 0 0]x0 [0 0 1] orientation: [1 1 1] [1] [1 1 0] [0] a(b(b(a(x1)))) = [0 1 0]x1 + [2] >= [0 0 0]x1 + [1] = a(c(a(b(x1)))) [0 0 0] [0] [0 0 0] [0] [1 0 1] [0] [1 0 1] a(c(x1)) = [0 0 0]x1 + [1] >= [0 0 0]x1 = c(c(a(x1))) [0 0 0] [0] [0 0 0] [1 0 0] [1 0 0] c(c(c(x1))) = [0 0 0]x1 >= [0 0 0]x1 = b(c(b(x1))) [0 0 1] [0 0 0] problem: a(c(x1)) -> c(c(a(x1))) c(c(c(x1))) -> b(c(b(x1))) Bounds Processor: bound: 1 enrichment: match automaton: final states: {5,1} transitions: a0(2) -> 3* b1(16) -> 17* b1(12) -> 13* b1(14) -> 15* b1(18) -> 19* b0(2) -> 6* b0(7) -> 5* c0(3) -> 4* c0(4) -> 1* c0(6) -> 7* f30() -> 2* c1(17) -> 18* c1(13) -> 14* 19 -> 4* 4 -> 12* 1 -> 3* 3 -> 16* 15 -> 1* problem: Qed