W3C home > Mailing lists > Public > ietf-http-wg-old@w3.org > May to August 1996

Re: Sticky headers and pipelining (was: Sticky header draft -- as an attachment)

From: Roy T. Fielding <fielding@liege.ICS.UCI.EDU>
Date: Wed, 07 Aug 1996 21:49:45 -0700
To: Paul Leach <paulle@microsoft.com>
Cc: 'http-wg' <http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com>
Message-Id: <9608072149.aa05462@paris.ics.uci.edu>
> The mechanism for that in the draft is that the client sends the header
> name and an empty value, which means that, even though there was a value
> for that header in the last message, this message should be interpreted
> as if the header with that field-name is not present in the message.

Ummm, I guess this is one of those things that should have been said
in the section on message field parsing....

An empty header field value has a meaning which is distinct from
a nonexistant header field.  An analogy is a variable in Perl --
no header field is equivalent to a value of undefined (a null pointer),
whereas a header field with an empty or whitespace-only value is equivalent
to an empty value (a pointer to a zero-length data segment).  Whether or
not those two have equivalent semantics is dependent on the definition
of the header field, just as

   Accept:

means accept nothing (if no other Accept headers are in the message)
and no Accept header field means accept anything.

> There must be some mechanism like this, independent of the semantics of
> any request header, in order for sticky headers to work at all.

Time to look for another mechanism...

  Connection: sticky
  Sticky: reset="Accept"

and assorted other yucky ideas come to mind.

BTW, while we are on the topic, I would prefer that the two unrelated
concepts of sticky headers and short header names be in two separate
drafts.  They should be evaluated independently.


 ...Roy T. Fielding
    Department of Information & Computer Science    (fielding@ics.uci.edu)
    University of California, Irvine, CA 92697-3425    fax:+1(714)824-4056
    http://www.ics.uci.edu/~fielding/
Received on Wednesday, 7 August 1996 22:02:24 EDT

This archive was generated by hypermail pre-2.1.9 : Wednesday, 24 September 2003 06:32:06 EDT