anchor.diff:  
   ## Data Structures
   
  -<!--### Choice (object)-->
  -<!--    + choice (string) - Text-->
  -<!--    + url (string) - Choice URL-->
  -<!--    + votes (number) - Number of votes-->
  -
  -<!--### Question (object)-->
  -<!--      + question (string) - Text of the question-->
  -<!--      + published_at (string) - An ISO8601 date when the question was published.-->
  -<!--      + url (string, required) - URL -->
  -<!--      + choices (array[Choice]) - An array of Choice objects.-->
   
   # REST API
   
  
positive.code: + Request (application/json)
  
          {
  "entities": [
      {
           "type": "Room",
           "isPattern": "true",
           "id": ".*"
      }
      ],
      "attributes": [
       "temperature"
      ],
      "reference": "http://localhost:8080/accumulate",
      "duration": "P1M"
   }
  
  + Response 201 (application/json)
  
      + Headers
  
              Location: /ngsi9
  
      + Body
  
              {
    "duration": "P1M",
      "subscriptionId": "52a745e011f5816465943d59"
    }
    
  ### Update Subscription to Context availability operation [POST /updateContextAvailabilitySubscription]
  
  
negative.code: FORMAT: 1A
  HOST: https://app.apiary.io/ngsi9
  TITLE: IoT Discovery GE Open API Specification
  DATE: 17/05/2016
  
  # FIWARE NGSI-9 API Core (v1)
  
  