HTTP/1.1, part 4: Conditional Requests
draft-ietf-httpbis-p4-conditional-20

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HTTPbis Working Group                                   R. Fielding, Ed.
Internet-Draft                                                     Adobe
Obsoletes: 2616 (if approved)                              Y. Lafon, Ed.
Intended status: Standards Track                                     W3C
Expires: January 17, 2013                                J. Reschke, Ed.
                                                              greenbytes
                                                           July 16, 2012

                 HTTP/1.1, part 4: Conditional Requests
                  draft-ietf-httpbis-p4-conditional-20

Abstract

   The Hypertext Transfer Protocol (HTTP) is an application-level
   protocol for distributed, collaborative, hypertext information
   systems.  This document defines HTTP/1.1 conditional requests,
   including metadata header fields for indicating state changes,
   request header fields for making preconditions on such state, and
   rules for constructing the responses to a conditional request when
   one or more preconditions evaluate to false.

Editorial Note (To be removed by RFC Editor)

   Discussion of this draft takes place on the HTTPBIS working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   <http://lists.w3.org/Archives/Public/ietf-http-wg/>.

   The current issues list is at
   <http://tools.ietf.org/wg/httpbis/trac/report/3> and related
   documents (including fancy diffs) can be found at
   <http://tools.ietf.org/wg/httpbis/>.

   The changes in this draft are summarized in Appendix D.1.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference

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Internet-Draft              HTTP/1.1, Part 4                   July 2012

   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 17, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Conformance and Error Handling . . . . . . . . . . . . . .  4
     1.2.  Syntax Notation  . . . . . . . . . . . . . . . . . . . . .  5
   2.  Validators . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Weak versus Strong . . . . . . . . . . . . . . . . . . . .  6
     2.2.  Last-Modified  . . . . . . . . . . . . . . . . . . . . . .  7
       2.2.1.  Generation . . . . . . . . . . . . . . . . . . . . . .  8
       2.2.2.  Comparison . . . . . . . . . . . . . . . . . . . . . .  8
     2.3.  ETag . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
       2.3.1.  Generation . . . . . . . . . . . . . . . . . . . . . . 10
       2.3.2.  Comparison . . . . . . . . . . . . . . . . . . . . . . 11
       2.3.3.  Example: Entity-tags varying on Content-Negotiated