title: Why Different Etags for Different Representations of the Same Resource?
body: <p>I understand the use of etags for optimistic concurrency control (e.g. in a RESTful style of architecture), and I've read that etags should be different for different representations of the same resource. Why is that?</p>
  
  <p>Ultimately aren't we interested in knowing if the <em>resource</em> has changed so we can handle concurrent modifications? I'm having a hard time even envisioning when a resource's representation would change without the resource itself changing, so I'm obviously missing some basic understanding.</p>