anchor.diff:  
   + Response 204
   
  -# Group Registrations
  -
  -Context Registration allows to associate external services to context data. One of the main
  -use cases of this functionality is the association of Context Providers.
  -
  -A context registration is represented by a JSON object with the following fields:
  -
  -+ `id`       : Unique identifier assigned to the registration. Automatically generated at creation
  -  time.
  -+ `subject`  : Object that describes the subject of the registration.
  -+ `callback` : URL which denotes the end-point of the registered service. It is optional, as it can
  -  be undefined under certain conditions, for instance, transient unavailability of the provider.
  -+ `metadata` : An optional JSON object which allows to associate extra metadata properties to the
  -  registration.
  -  It must follow the same representation conventions as context attribute metadata
  -  (See JSON Attribute Representation). 
  -+ `duration` : Duration of the registration in ISO8601 format. Default duration is infinite.
  -
  -A `subject` contains the following subfields:
  -
  -+ `entities`: A list of objects, each one composed of the following subfields (`id`/`idPattern` or
  -  type must be present):
  -    + `id` or `idPattern`: Id or pattern of the affected entities. Both cannot be set at the same
  -      time, but one of them must be set.
  -    + `type`: Type of the affected entities (optional).
  -+ `attributes`: List of attributes to be provided (if not specified, all attributes).
  -
  -## Registration list [/v2/registrations]
  -
  -### Retrieve registrations [GET /v2/registrations]
  -
  -Lists all the registrations present in the system.
  -
  -Response:
  -
  -* Successful operation uses 200 OK
  -* Errors use a non-2xx and (optionally) an error payload. See subsection on "Error Responses" for
  -  more details.
  -
  -+ Response 200
  -
  -        [
  -          {
  -            "id": "abcdefg",
  -            "subject": {
  -              "entities": [
  -                {
  -                  "id": "Bcn_Welt",
  -                  "type": "Room"
  -                }
  -              ],
  -              "attributes": [
  -                "temperature"
  -              ]
  -            },
  -            "callback": "http://weather.example.com/ngsi",
  -            "metadata": {
  -              "providingService": {
  -                 "value": "weather.example.com",
  -                 "type": "none"
  -               },
  -              "providingAuthority": {
  -                 "value": "AEMET - Spain",
  -                 "type": "none"
  -               }
  -            },
  -            "duration": "PT1M"
  -          }
  -        ]
  -
  -### Create a new context provider registration [POST /v2/registrations]
  -
  -Creates a new registration. This is typically used for associating context providers
  -to certain data.
  -The registration is represented by a JSON object as described at the beginning of this section.
  -
  -Response:
  -
  -* Successful operation uses 201 Created
  -* Errors use a non-2xx and (optionally) an error payload. See subsection on "Error Responses" for
  -  more details.
  -
  -+ Request (application/json)
  -
  -        {
  -          "subject": {
  -            "entities": [
  -              {
  -                "id": "room2",
  -                "type": "Room"
  -              }
  -            ],
  -            "attributes": [
  -              "humidity"
  -            ]
  -          },
  -          "callback":  "http://localhost:1234",
  -          "metadata" : {
  -            "provider": {
  -              "value": "example.com"
  -            }
  -          },
  -          "duration": "PT1M"
  -        }
  -
  -+ Response 201
  -
  -    + Headers
  -
  -            Location: /v2/registrations/abcde98765
  -
  -## Registration By ID [/v2/registrations/{registrationId}]
  -
  -### Retrieve context provider registration [GET /v2/registrations/{registrationId}]
  -
  -The response is the registration represented by a JSON object as described at the beginning of this
  -section.
  -
  -Response:
  -
  -* Successful operation uses 200 OK
  -* Errors use a non-2xx and (optionally) an error payload. See subsection on "Error Responses" for
  -  more details.
  -
  -+ Parameters
  -    + registrationId: abcdef (required, string) - registration Id.
  -
  -+ Response 200 (application/json)
  -
  -        {
  -          "id": "abcde",
  -          "subject": {
  -            "entities": [
  -              {
  -                "id": "room2",
  -                "type": "Room"
  -              }
  -            ],
  -            "attributes": [
  -              "humidity"
  -            ]
  -          },
  -          "callback":  "http://localhost:1234",
  -          "duration": "PT1M"
  -        }
  -
  -### Update context provider registration [PATCH /v2/registrations/{registrationId}]
  -
  -Only the fields included in the request are updated in the registration.
  -
  -Response:
  -
  -* Successful operation uses 204 No Content
  -* Errors use a non-2xx and (optionally) an error payload. See subsection on "Error Responses" for
  -  more details.
  -
  -+ Parameters
  -    + registrationId: abcdef (required, string) - registration Id.
  -
  -+ Request (application/json)
  -
  -        {
  -          "duration": "PT1M"
  -        }
  -
  -+ Response 204
  -
  -### Delete context provider registration [DELETE /v2/registrations/{registrationId}]
  -
  -Cancels registration.
  -
  -Response:
  -
  -* Successful operation uses 204 No Content
  -* Errors use a non-2xx and (optionally) an error payload. See subsection on "Error Responses" for
  -  more details.
  -
  -+ Parameters
  -    + registrationId: abcdef (required, string) - registration Id.
  -
  -+ Response 204
  -
   # Group Batch Operations
   
   ### Update [POST /v2/op/update]
  
positive.code:       "type": "Room",
        "temperature": {
          "value": 24,
          "type": "none",
          "metadata": {}
        }
      }
  
negative.code:              "metadata": {
                 "accuracy": {
                   "value": 2,
                   "type": "Number"
                 },
                 "timestamp": {
                   "value": "2015-06-04T07:20:27.378Z",
  