title: Best way to model identifiers (unique id) in JSON
body: <p>When modelling JSON data we have usually to deal with unique objects identifiers. We could model them as (i) <em>key</em> (or <em>property</em>) or as (ii) <em>value</em>. Which is the best solution, if any, or what are pros and cons? Here there is an example.</p>
  
  <p>Identifier as key:</p>
  
  <pre><code>[
    {
      "1": {
        "tel": "tel1",
        "e-mail": "mail2"
      }
    },
    {
      "2": {
        "tel": "tel2",
        "e-mail": "mail2"
      }
    }
  ]
  </code></pre>
  
  <p>Identifier as value of <code>id</code> key:</p>
  
  <pre><code>[
    {
      "id": 1,
      "tel": "tel1",
      "e-mail": "mail2"
    },
    {
      "id": 1,
      "tel": "tel2",
      "e-mail": "mail2"
    }
  ]
  </code></pre>