YES Problem: a(a(x1)) -> a(b(c(c(x1)))) c(a(x1)) -> x1 c(b(x1)) -> a(a(x1)) Proof: String Reversal Processor: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) DP Processor: DPs: a#(a(x1)) -> b#(a(x1)) b#(c(x1)) -> a#(x1) b#(c(x1)) -> a#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) TDG Processor: DPs: a#(a(x1)) -> b#(a(x1)) b#(c(x1)) -> a#(x1) b#(c(x1)) -> a#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) graph: b#(c(x1)) -> a#(a(x1)) -> a#(a(x1)) -> b#(a(x1)) b#(c(x1)) -> a#(x1) -> a#(a(x1)) -> b#(a(x1)) a#(a(x1)) -> b#(a(x1)) -> b#(c(x1)) -> a#(a(x1)) a#(a(x1)) -> b#(a(x1)) -> b#(c(x1)) -> a#(x1) Arctic Interpretation Processor: dimension: 2 usable rules: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) interpretation: [b#](x0) = [2 1]x0 + [0], [a#](x0) = [0 1]x0 + [0], [1 0] [0] [b](x0) = [2 1]x0 + [0], [-& 0 ] [0] [c](x0) = [0 -&]x0 + [3], [-& 0 ] [0] [a](x0) = [0 1 ]x0 + [3] orientation: a#(a(x1)) = [1 2]x1 + [4] >= [1 2]x1 + [4] = b#(a(x1)) b#(c(x1)) = [1 2]x1 + [4] >= [0 1]x1 + [0] = a#(x1) b#(c(x1)) = [1 2]x1 + [4] >= [1 2]x1 + [4] = a#(a(x1)) [0 1] [3] [0 1] [3] a(a(x1)) = [1 2]x1 + [4] >= [1 2]x1 + [4] = c(c(b(a(x1)))) [0 -&] [3] a(c(x1)) = [1 0 ]x1 + [4] >= x1 = x1 [0 1] [3] [0 1] [3] b(c(x1)) = [1 2]x1 + [4] >= [1 2]x1 + [4] = a(a(x1)) problem: DPs: a#(a(x1)) -> b#(a(x1)) b#(c(x1)) -> a#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) Restore Modifier: DPs: a#(a(x1)) -> b#(a(x1)) b#(c(x1)) -> a#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) EDG Processor: DPs: a#(a(x1)) -> b#(a(x1)) b#(c(x1)) -> a#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) graph: b#(c(x1)) -> a#(a(x1)) -> a#(a(x1)) -> b#(a(x1)) a#(a(x1)) -> b#(a(x1)) -> b#(c(x1)) -> a#(a(x1)) Arctic Interpretation Processor: dimension: 3 usable rules: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) interpretation: [b#](x0) = [0 -& 0 ]x0 + [0], [a#](x0) = [-& -& 0 ]x0 + [0], [0 -& 0 ] [0] [b](x0) = [0 0 1 ]x0 + [0] [0 -& 0 ] [0], [0 0 -&] [0] [c](x0) = [0 -& 0 ]x0 + [0] [0 1 -&] [1], [-& 0 -&] [0] [a](x0) = [0 1 -&]x0 + [1] [-& 0 -&] [0] orientation: a#(a(x1)) = [-& 0 -&]x1 + [0] >= [-& 0 -&]x1 + [0] = b#(a(x1)) b#(c(x1)) = [0 1 -&]x1 + [1] >= [-& 0 -&]x1 + [0] = a#(a(x1)) [0 1 -&] [1] [0 1 -&] [1] a(a(x1)) = [1 2 -&]x1 + [2] >= [1 2 -&]x1 + [2] = c(c(b(a(x1)))) [0 1 -&] [1] [0 1 -&] [1] [0 -& 0 ] [0] a(c(x1)) = [1 0 1 ]x1 + [1] >= x1 = x1 [0 -& 0 ] [0] [0 1 -&] [1] [0 1 -&] [1] b(c(x1)) = [1 2 0 ]x1 + [2] >= [1 2 -&]x1 + [2] = a(a(x1)) [0 1 -&] [1] [0 1 -&] [1] problem: DPs: a#(a(x1)) -> b#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) Restore Modifier: DPs: a#(a(x1)) -> b#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) EDG Processor: DPs: a#(a(x1)) -> b#(a(x1)) TRS: a(a(x1)) -> c(c(b(a(x1)))) a(c(x1)) -> x1 b(c(x1)) -> a(a(x1)) graph: Qed