YES Problem: a(b(x)) -> b(a(a(x))) b(c(x)) -> c(b(b(x))) c(a(x)) -> a(c(c(x))) u(a(x)) -> x v(b(x)) -> x w(c(x)) -> x a(u(x)) -> x b(v(x)) -> x c(w(x)) -> x Proof: Matrix Interpretation Processor: dim=1 interpretation: [w](x0) = x0 + 4, [v](x0) = 12x0, [u](x0) = 12x0 + 1, [c](x0) = x0, [a](x0) = x0, [b](x0) = x0 orientation: a(b(x)) = x >= x = b(a(a(x))) b(c(x)) = x >= x = c(b(b(x))) c(a(x)) = x >= x = a(c(c(x))) u(a(x)) = 12x + 1 >= x = x v(b(x)) = 12x >= x = x w(c(x)) = x + 4 >= x = x a(u(x)) = 12x + 1 >= x = x b(v(x)) = 12x >= x = x c(w(x)) = x + 4 >= x = x problem: a(b(x)) -> b(a(a(x))) b(c(x)) -> c(b(b(x))) c(a(x)) -> a(c(c(x))) v(b(x)) -> x b(v(x)) -> x Matrix Interpretation Processor: dim=3 interpretation: [1 1 0] [1] [v](x0) = [0 1 1]x0 + [0] [0 0 1] [0], [1 0 0] [0] [c](x0) = [0 0 0]x0 + [1] [0 1 1] [1], [1 0 0] [a](x0) = [0 1 0]x0 [0 1 0] , [b](x0) = x0 orientation: [1 0 0] [1 0 0] a(b(x)) = [0 1 0]x >= [0 1 0]x = b(a(a(x))) [0 1 0] [0 1 0] [1 0 0] [0] [1 0 0] [0] b(c(x)) = [0 0 0]x + [1] >= [0 0 0]x + [1] = c(b(b(x))) [0 1 1] [1] [0 1 1] [1] [1 0 0] [0] [1 0 0] [0] c(a(x)) = [0 0 0]x + [1] >= [0 0 0]x + [1] = a(c(c(x))) [0 2 0] [1] [0 0 0] [1] [1 1 0] [1] v(b(x)) = [0 1 1]x + [0] >= x = x [0 0 1] [0] [1 1 0] [1] b(v(x)) = [0 1 1]x + [0] >= x = x [0 0 1] [0] problem: a(b(x)) -> b(a(a(x))) b(c(x)) -> c(b(b(x))) c(a(x)) -> a(c(c(x))) String Reversal Processor: b(a(x)) -> a(a(b(x))) c(b(x)) -> b(b(c(x))) a(c(x)) -> c(c(a(x))) Bounds Processor: bound: 0 enrichment: match automaton: final states: {8,5,1} transitions: a0(2) -> 9* a0(4) -> 1* a0(3) -> 4* b0(7) -> 5* b0(2) -> 3* b0(6) -> 7* c0(10) -> 8* c0(2) -> 6* c0(9) -> 10* f60() -> 2* 1 -> 3* 5 -> 6* 8 -> 9* problem: Qed