anchor.diff:  %%
   %% JSON response looks like:
   %% ```
  -%% {"Access":[{"Node":"riak_moss@127.0.0.1",
  -%%             "Samples":[{"StartTime":"20120113T194510Z",
  -%%                         "EndTime":"20120113T194520Z",
  -%%                         "KeyRead":{"Count":1,
  -%%                                    "BytesOut":22},
  -%%                         "KeyWrite":{"Count":2,
  -%%                                     "BytesIn":44},
  -%%                        {"StartTime":"20120113T194520Z",
  -%%                         "EndTime":"20120113T194530Z",
  -%%                         "KeyRead":{"Count":3,
  -%%                                    "BytesOut":66},
  -%%                         "KeyWrite":{"Count":4,
  -%%                                     "BytesIn":88}
  -%%                       ]}
  -%%           ],
  +%% {"Access":{
  +%%            "Nodes":[{"Node":"riak_moss@127.0.0.1",
  +%%                      "Samples":[{"StartTime":"20120113T194510Z",
  +%%                                  "EndTime":"20120113T194520Z",
  +%%                                  "KeyRead":{"Count":1,
  +%%                                             "BytesOut":22},
  +%%                                  "KeyWrite":{"Count":2,
  +%%                                              "BytesIn":44}},
  +%%                                 {"StartTime":"20120113T194520Z",
  +%%                                  "EndTime":"20120113T194530Z",
  +%%                                  "KeyRead":{"Count":3,
  +%%                                             "BytesOut":66},
  +%%                                  "KeyWrite":{"Count":4,
  +%%                                              "BytesIn":88}}
  +%%                                ]}],
  +%%            "Errors":[]
  +%%           },
   %%  "Storage":"not_requested"}
   %% '''
   %%
  
positive.code: -define(KEY_ACCESS, 'Access').
  -define(KEY_STORAGE, 'Storage').
  -define(KEY_NODE, 'Node').
  -define(KEY_SAMPLE,  'Sample').
  -define(KEY_SAMPLES, 'Samples').
  -define(KEY_OPERATION, 'Operation').
  
negative.code: xml_access(Msg) when is_atom(Msg) ->
      [atom_to_list(Msg)];
  xml_access({Access, Errors}) ->
      Nodes = [{?KEY_NODE, [{name, Node}],
                [xml_sample(S, ?KEY_OPERATION, ?KEY_TYPE) || S <- Samples]}
               || {Node, Samples} <- Access],
      Errs = [ xml_sample_error(E, ?KEY_OPERATION, ?KEY_TYPE)
               || E <- Errors ],
      [{?KEY_NODES, Nodes},
       {?KEY_ERRORS, Errs}].
  
  xml_sample(Sample, SubType, TypeLabel) ->
      {value, {?START_TIME,S}, SampleS} =
  