title: JSON Schema oneOf properies filled
body: <p>How to set JSON Schema rule to say that exactly one of the properties have to be set and is required?</p>
  
  <p>I tried various ways to solve it like:</p>
  
  <pre><code>{
     "id":"#",
     "required":true,
     "additionalProperties":true,
     "type":"object",
     "properties":{
        "surname":{
           "id":"surname",
           "required":true,
           "type":"string"
        },
        "oneOf":[
           {
              "$ref":"#/definitions/station_id"
           },
           {
              "$ref":"#/definitions/station"
           }
        ]
     },
     "definitions":{
        "station_id":{
           "type":"integer"
        },
        "station":{
           "type":"string"
        }
     }
  }
  </code></pre>
  
  <p>But it never worked. What I need to do is to accept either station_id what is an integer or station what is a string name.</p>
  
  <p>Is there a way to do that, please?</p>