="#section-6">6</a>. Versioning</span>

    All successful requests MUST return an &#39;ETag&#39; header [<a href="#ref-HTTP">HTTP</a>] with, in
    the case of GET, the current version, in the case of PUT, the new
    version, and in case of DELETE, the version that was deleted. All
    successful GET requests MUST return an &#39;Expires: 0&#39; header. PUT and
    DELETE requests MAY have an &#39;If-Match&#39; request header [<a href="#ref-COND">COND</a>], and
    MUST fail with a 412 response code if tha