If header field and conditional precedence

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If header field and conditional precedence

Ken Murchison
Happy Holidays to All!

I'm trying to figure out where the If header field fits in the
precedence order outlined in:
http://tools.ietf.org/html/draft-ietf-httpbis-p4-conditional-21#section-5

I assume that the If header field should be evaluated in a step 0, but
my question is what should happen when the If header is present and
evaluates to true?  Should processing continue to step 3 or step 1?  In
other words, does If completely supersede If-Match, where a client
wishing to submit both a state token and an ETag MUST only use If, or is
a client allowed to submit a state token with If AND submit an ETag with
If-Match?

In text, the two options might look something like this:

    0.  When If is present, evaluate it:

        *  if true, continue to step 3

        *  if false, respond 412 (Precondition Failed)

    1.  When If is not present and If-Match is present,
        evaluate it:

    ...


OR


    0.  When If is present, evaluate it:

        *  if true, continue to step 1

        *  if false, respond 412 (Precondition Failed)

    1.  When If-Match is present, evaluate it:

    ...

--
Kenneth Murchison
Principal Systems Software Engineer
Carnegie Mellon University


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Re: If header field and conditional precedence

Julian Reschke
On 2012-12-23 22:00, Ken Murchison wrote:
> Happy Holidays to All!
> ...


I would recommend that you re-send to the HTTP mailing list. Are new
conditional headers an extension point that needs to be described
specifically? It seems that a specification that registers a new
conditional header needs needs to define how it interacts with the
others; and thus we probably should add this to the "considerations for
new header fields" part...

Best regards, Julian

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Re: If header field and conditional precedence

Ken Murchison
Julian Reschke wrote:

> On 2012-12-23 22:00, Ken Murchison wrote:
>> Happy Holidays to All!
>> ...
>
>
> I would recommend that you re-send to the HTTP mailing list. Are new
> conditional headers an extension point that needs to be described
> specifically? It seems that a specification that registers a new
> conditional header needs needs to define how it interacts with the
> others; and thus we probably should add this to the "considerations for
> new header fields" part...

Hi Julian,

HTTPbis, part 4 already has text stating that extensions need to define
how additional conditional headers are expected to play with others,
which is why I brought my question to the WebDAV list.  I can certainly
take it to the HTTPbis list of you still feel that is the best place.

   "Any extension to HTTP/1.1 that defines additional conditional request
    header fields ought to define its own expectations regarding the
    order for evaluating such fields in relation to those defined in this
    document and other conditionals that might be found in practice."



--
Kenneth Murchison
Principal Systems Software Engineer
Carnegie Mellon University