W3C home > Mailing lists > Public > ietf-http-wg@w3.org > July to September 2009

requested resource / entity / representation / variant again..

From: Henrik Nordstrom <henrik@henriknordstrom.net>
Date: Tue, 21 Jul 2009 18:27:26 +0200
To: HTTP Working Group <ietf-http-wg@w3.org>
Message-Id: <1248193646.23873.453.camel@localhost.localdomain>
The "resource" discussion again highlighted the fuzziness on what
"requested resource" really means.

When reading the specs again I can only agree that it's still quite
fuzzy, but for other reasons. The way "requested resource" vs
"representation" is currently used confuses matters a bit.

Intuitively "requested resource" should refer to the resource identified
by the Request-URI. But in fact it's not..

To me it seems that quite many of the places which today say "requested
resource" maybe should say "requested representation" (if one can say
anything like that) to align them better with the language used for
server driven content negotiation, or perhaps we should use the term
"variant" consistently pretty much anywhere we say "requested resource"
or "selected representation". But neither is good if there exists
resources with no representations associated...

If not that then the concept of "requested resource" and language used
for describing server driven content negotiation both needs to be
adjusted/clarified to connect them together.

Some examples:
p3 4. Content Negotiation

        "content negotiation" -- the process of selecting the best
        representation for a given response when there are multiple
        representations available.

p3 4.1 Server-driven Negotiation

        ... select a representation ...

etc, quite consistent use representation to identify what was selected
and acted upon. Oddly this chapter talks very little about resources
however..

However, in other areas "requested resource" or even "variant" (wasn't
variant supposed to be killed some time ago?) is used for referring to
pretty much the same thing. For example

p4 6.5 If-Unmodified-Since

        If the requested resource has not been modified since ...

p4 6.6 Last-Modified

        ... the variant was last modified.
        

p2 8.2.1 200 OK

        GET & HEAD ... the requested resource ...



While in some other areas "requested resource" seems to refer to the
"resource" identified by the URI, regardless of any content negotiation
taking place.

And yes, Server driven content negotiation IS confusing to terminology
as it causes the notion of a resource to be quite twisted and in reality
is often implemented as several independent resources sharing the same
URI...

Sorry, head a litte dizzy now trying to sort some sense out of these
terms when content negotiation is used.. can't really say I see a light
yet.

Regards
Henrik
Received on Tuesday, 21 July 2009 16:28:02 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Friday, 27 April 2012 06:51:08 GMT