title: mongoose - schemas included : Model or ObjectId & Ref
body: <p>I'm trying to migrate a database from Wakanda to MongoDb - mongoose (I never work on it) and I encountered few issues with modelisation.</p>
  <p>I have many schemas which included other ones and I don't find which method is the best between :</p>
  <p>Models :</p>
  <pre><code>var schemaA = mongoose.Schema({
      dossier: {type: mongoose.model.Dossier, index: true},
  });
  </code></pre>
  <p>and ObjectId &amp; Ref :</p>
  <pre><code>var schemaA = mongoose.Schema({
      dossier:  {type: Schema.Types.ObjectId, ref: 'Dossier'} ,
  });
  </code></pre>
  <p>Thanks for your advices</p>