2.2.4 ResourceTag Header
The ResourceTag header contains a ResourceTag. This identifier is available in a read-only property that can be requested, and is returned in the body of the result for a PROPFIND method, but it is also returned in a ResourceTag header in the response to a successful GET, HEAD, or POST operation.
ResourceTag-Header = "ResourceTag" ":" ResourceTag ResourceTag = "rt:" DocumentID "@" 11DIGIT
The ResourceTag is an absolute-URI, as defined in [RFC3986], using the unregistered "rt" scheme. The value consists of a DocumentID followed by the at sign (@) followed by 11 decimal digits containing a version number for the resource. The ResourceTag header usage is specified in sections 18.104.22.168 and 22.214.171.124.