YES(?,O(n^2))
TRS:
 {
  app(app(plus(), app(s(), x)), y) -> app(s(), app(app(plus(), x), y)),
                      app(id(), x) -> x,
                  app(plus(), 0()) -> id()
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
    app(app(plus(), app(s(), x)), y) -> app(s(), app(app(plus(), x), y)),
                        app(id(), x) -> x,
                    app(plus(), 0()) -> id()
   }
  Matrix Interpretation:
   Interpretation class: triangular
         [0]
   [s] = [0]
   
         [3]
   [0] = [2]
   
            [1]
   [plus] = [0]
   
          [1]
   [id] = [3]
   
         [X3]  [X1]    [1 1][X3]   [1 0][X1]   [0]
   [app]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [2]
   
   
   Qed