title: ASN.1 AUTOMATIC TAGS and EXTENSIBILITY IMPLIED Attributes
body: <p>I have been presented with an ASN.1 document that includes two encoding/decoding attributes; </p>
  
  <ul>
  <li>AUTOMATIC TAGS
  
  <ul>
  <li>My understanding; the tags are defined automatically using the encoding rules unless a tag notation is present in the definition</li>
  </ul></li>
  <li>EXTENSIBILITY IMPLIED
  
  <ul>
  <li>My understanding; types may have elements that are not defined within the ASN.1 document. If found, the encoder should silently ignore. <em>Additionally, my decoder should also be ready to handle values with unspecified tags.</em></li>
  </ul></li>
  </ul>
  
  <p><strong>Q1:</strong> Are my understandings above correct?</p>
  
  <p><strong>Q2:</strong> w.r.t AUTOMATIC TAGS; defining automatically seems infeasible (obviously not...) but my understanding is that <code>someEncoder</code> would therefore assign <code>SomeType.class</code> with tag (for example) <code>0xBB</code>; how does <code>someDecoder</code> know how to decode <code>0xBB</code> back to <code>SomeType</code>? </p>
  
  <p><strong>Q2:</strong> w.r.t unspecified tags; once again, I am unsure how to pass an unspecified Tag back to something else. </p>