anchor.diff:  %-define(DEBUG, 1).
   -include("debug.hrl").
   
  -
  -% XXX: or use "application/octet-stream" Content-Type instead of
  -% "application/protobuf"?
   
   % XXX: set charset=UTF-8 in "Content-Type" response header for text (Piq), Json
   % and XML responses?
  
positive.code:                 [
                      {"text/plain", get_piqi_piq},
                      {"application/json", get_piqi_json},
                      {"application/protobuf", get_piqi_pb}
                  ];
              'POST' ->
                  [
                      {"application/json", unused_value},
                      {"application/protobuf", unused_value},
                      {"text/plain", unused_value}
                  ]
          end,
  
negative.code:     IsKnownType =
          case wrq:get_req_header("content-type", ReqData) of
              "application/json" -> true;
              "application/x-protobuf" -> true;
              % allow content-type to be undefined when the body is empty
              'undefined' when IsEmptyBody -> true;
              _ -> false
  