YES Problem: s(a()) -> a() s(s(x)) -> x s(f(x,y)) -> f(s(y),s(x)) s(g(x,y)) -> g(s(x),s(y)) f(x,a()) -> x f(a(),y) -> y f(g(x,y),g(u,v)) -> g(f(x,u),f(y,v)) g(a(),a()) -> a() Proof: DP Processor: DPs: s#(f(x,y)) -> s#(x) s#(f(x,y)) -> s#(y) s#(f(x,y)) -> f#(s(y),s(x)) s#(g(x,y)) -> s#(y) s#(g(x,y)) -> s#(x) s#(g(x,y)) -> g#(s(x),s(y)) f#(g(x,y),g(u,v)) -> f#(y,v) f#(g(x,y),g(u,v)) -> f#(x,u) f#(g(x,y),g(u,v)) -> g#(f(x,u),f(y,v)) TRS: s(a()) -> a() s(s(x)) -> x s(f(x,y)) -> f(s(y),s(x)) s(g(x,y)) -> g(s(x),s(y)) f(x,a()) -> x f(a(),y) -> y f(g(x,y),g(u,v)) -> g(f(x,u),f(y,v)) g(a(),a()) -> a() Matrix Interpretation Processor: dim=1 usable rules: s(a()) -> a() s(s(x)) -> x s(f(x,y)) -> f(s(y),s(x)) s(g(x,y)) -> g(s(x),s(y)) f(x,a()) -> x f(a(),y) -> y f(g(x,y),g(u,v)) -> g(f(x,u),f(y,v)) g(a(),a()) -> a() interpretation: [g#](x0, x1) = 2x1, [f#](x0, x1) = x0 + x1, [s#](x0) = x0, [g](x0, x1) = 3x0 + 2x1 + 5/2, [f](x0, x1) = x0 + x1 + 1/2, [s](x0) = x0, [a] = 1 orientation: s#(f(x,y)) = x + y + 1/2 >= x = s#(x) s#(f(x,y)) = x + y + 1/2 >= y = s#(y) s#(f(x,y)) = x + y + 1/2 >= x + y = f#(s(y),s(x)) s#(g(x,y)) = 3x + 2y + 5/2 >= y = s#(y) s#(g(x,y)) = 3x + 2y + 5/2 >= x = s#(x) s#(g(x,y)) = 3x + 2y + 5/2 >= 2y = g#(s(x),s(y)) f#(g(x,y),g(u,v)) = 3u + 2v + 3x + 2y + 5 >= v + y = f#(y,v) f#(g(x,y),g(u,v)) = 3u + 2v + 3x + 2y + 5 >= u + x = f#(x,u) f#(g(x,y),g(u,v)) = 3u + 2v + 3x + 2y + 5 >= 2v + 2y + 1 = g#(f(x,u),f(y,v)) s(a()) = 1 >= 1 = a() s(s(x)) = x >= x = x s(f(x,y)) = x + y + 1/2 >= x + y + 1/2 = f(s(y),s(x)) s(g(x,y)) = 3x + 2y + 5/2 >= 3x + 2y + 5/2 = g(s(x),s(y)) f(x,a()) = x + 3/2 >= x = x f(a(),y) = y + 3/2 >= y = y f(g(x,y),g(u,v)) = 3u + 2v + 3x + 2y + 11/2 >= 3u + 2v + 3x + 2y + 5 = g(f(x,u),f(y,v)) g(a(),a()) = 15/2 >= 1 = a() problem: DPs: TRS: s(a()) -> a() s(s(x)) -> x s(f(x,y)) -> f(s(y),s(x)) s(g(x,y)) -> g(s(x),s(y)) f(x,a()) -> x f(a(),y) -> y f(g(x,y),g(u,v)) -> g(f(x,u),f(y,v)) g(a(),a()) -> a() Qed