title: Accessing versions/revisions of an object in a RESTful API
body: <p>While designing a RESTful API we came across the problem of how to access different versions of the "same object". Let us say a page object is identified by a unique key and accessed by GET /api/page/pagekey. It can be updated by sending PUT /api/page/pagekey and an appropriate document in the body. </p>
  
  <p>Now our system keeps track of old versions of the page, that we also want to access via the API. Let us assume that an older version of the document is version 1. There seem to be at least two ways to design the API to access this particular version of the page:</p>
  
  <ol>
  <li>GET /api/page/pagekey/1</li>
  <li>GET /api/page/pagekey?version=1</li>
  </ol>
  
  <p>The first variant renders the particular version as its own resource; the second variant gives the existing resource an optional version context.</p>
  
  <ul>
  <li>Is variant (1) or (2) a better solution? Or is there an even better way to do it?</li>
  <li>In variant (1) a request for a version number that does not exist e.g. /api/page/pagekey/7 could trigger a HTTP 404 Not Found, which is quit handy. Would this also be a valid status response when considering variant (2), where we only change the context "version" of the existing resource, that would without the version parameter return a HTTP 200 Ok response?</li>
  </ul>