Re: ISSUE VARY: Proposed wording

Jeffrey Mogul (mogul@pa.dec.com)
Wed, 09 Jul 97 17:50:23 MDT 

Proposed changes to Section 13.6, 4th Paragraph:

RFC2068:

    The Vary header field may also inform the cache that the
    representation was selected using criteria not limited to the
    request-headers; in this case, a cache MUST NOT use the response in
    a reply to a subsequent request unless the cache relays the new
    request to the origin server in a conditional request and the
    server responds with 304 (Not Modified), including an entity tag or
    Content-Location that indicates which entity should be used.

Henrik proposed:

    The Vary header field MUST also inform the cache that the
    representation was selected using criteria not limited to the
    request-headers; in this case, a cache MUST NOT use the response in
    a reply to a subsequent request unless the cache relays the new
    request to the origin server in a conditional request and the
    server responds with 304 (Not Modified), including an entity tag or
    Content-Location that indicates which entity should be used.
    
Koen changed one word:

    The Vary header field MUST also inform the cache *if* the
    representation was selected using criteria not limited to the
    request-headers; in this case, a cache MUST NOT use the response in
    a reply to a subsequent request unless the cache relays the new
    request to the origin server in a conditional request and the
    server responds with 304 (Not Modified), including an entity tag or
    Content-Location that indicates which entity should be used.
    
I think the first part is still somewhat misleading.  How about:

    If the representation was selected using criteria not limited to
    the request-headers, then the server MUST include a "Vary: *"
    header field in the response.
    In this case, a cache MUST NOT use the response in
    a reply to a subsequent request unless the cache relays the new
    request to the origin server in a conditional request and the
    server responds with 304 (Not Modified), including an entity tag or
    Content-Location that indicates which entity should be used.

As long as we are going to say MUST, we should be explicit about
what the requirement is.

-Jeff