YES Problem: a(c(d(x))) -> c(x) u(b(d(d(x)))) -> b(x) v(a(a(x))) -> u(v(x)) v(a(c(x))) -> u(b(d(x))) v(c(x)) -> b(x) w(a(a(x))) -> u(w(x)) w(a(c(x))) -> u(b(d(x))) w(c(x)) -> b(x) Proof: String Reversal Processor: d(c(a(x))) -> c(x) d(d(b(u(x)))) -> b(x) a(a(v(x))) -> v(u(x)) c(a(v(x))) -> d(b(u(x))) c(v(x)) -> b(x) a(a(w(x))) -> w(u(x)) c(a(w(x))) -> d(b(u(x))) c(w(x)) -> b(x) KBO Processor: weight function: w0 = 1 w(w) = w(v) = w(u) = w(b) = w(a) = w(c) = w(d) = 1 precedence: u > v > a > b > w > c > d problem: Qed