source: draft-ietf-httpbis/latest/p2-semantics.xml @ 965

Last change on this file since 965 was 965, checked in by fielding@…, 9 years ago

Addresses #109: Clarify entity / representation / variant terminology

Removed entity-header adjective and ABNF and clarified distinction
between payload and representation.

Uncapitalize the phrase effective request URI so that it doesn't
dominate the prose, and define the term "target resource" to be
used instead of the "resource identified by the effective request URI".

  • Property svn:eol-style set to native
File size: 160.4 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "July">
16  <!ENTITY ID-YEAR "2010">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY caching-combining-headers  "<xref target='Part6' x:rel='#combining.headers' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness'
77xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-explicit               "<xref target='Part6' x:rel='#calculating.freshness.lifetime'
79xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p6-combine               "<xref target='Part6' x:rel='#combining.headers'
81xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82]>
83<?rfc toc="yes" ?>
84<?rfc symrefs="yes" ?>
85<?rfc sortrefs="yes" ?>
86<?rfc compact="yes"?>
87<?rfc subcompact="no" ?>
88<?rfc linkmailto="no" ?>
89<?rfc editing="no" ?>
90<?rfc comments="yes"?>
91<?rfc inline="yes"?>
92<?rfc rfcedstyle="yes"?>
93<?rfc-ext allow-markup-in-artwork="yes" ?>
94<?rfc-ext include-references-in-index="yes" ?>
95<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
96     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
97     xmlns:x='http://purl.org/net/xml2rfc/ext'
98     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
99<front>
100
101  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
102
103  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
104    <organization abbrev="Day Software">Day Software</organization>
105    <address>
106      <postal>
107        <street>23 Corporate Plaza DR, Suite 280</street>
108        <city>Newport Beach</city>
109        <region>CA</region>
110        <code>92660</code>
111        <country>USA</country>
112      </postal>
113      <phone>+1-949-706-5300</phone>
114      <facsimile>+1-949-706-5305</facsimile>
115      <email>fielding@gbiv.com</email>
116      <uri>http://roy.gbiv.com/</uri>
117    </address>
118  </author>
119
120  <author initials="J." surname="Gettys" fullname="Jim Gettys">
121    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
122    <address>
123      <postal>
124        <street>21 Oak Knoll Road</street>
125        <city>Carlisle</city>
126        <region>MA</region>
127        <code>01741</code>
128        <country>USA</country>
129      </postal>
130      <email>jg@freedesktop.org</email>
131      <uri>http://gettys.wordpress.com/</uri>
132    </address>
133  </author>
134 
135  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
136    <organization abbrev="HP">Hewlett-Packard Company</organization>
137    <address>
138      <postal>
139        <street>HP Labs, Large Scale Systems Group</street>
140        <street>1501 Page Mill Road, MS 1177</street>
141        <city>Palo Alto</city>
142        <region>CA</region>
143        <code>94304</code>
144        <country>USA</country>
145      </postal>
146      <email>JeffMogul@acm.org</email>
147    </address>
148  </author>
149
150  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
151    <organization abbrev="Microsoft">Microsoft Corporation</organization>
152    <address>
153      <postal>
154        <street>1 Microsoft Way</street>
155        <city>Redmond</city>
156        <region>WA</region>
157        <code>98052</code>
158        <country>USA</country>
159      </postal>
160      <email>henrikn@microsoft.com</email>
161    </address>
162  </author>
163
164  <author initials="L." surname="Masinter" fullname="Larry Masinter">
165    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
166    <address>
167      <postal>
168        <street>345 Park Ave</street>
169        <city>San Jose</city>
170        <region>CA</region>
171        <code>95110</code>
172        <country>USA</country>
173      </postal>
174      <email>LMM@acm.org</email>
175      <uri>http://larry.masinter.net/</uri>
176    </address>
177  </author>
178 
179  <author initials="P." surname="Leach" fullname="Paul J. Leach">
180    <organization abbrev="Microsoft">Microsoft Corporation</organization>
181    <address>
182      <postal>
183        <street>1 Microsoft Way</street>
184        <city>Redmond</city>
185        <region>WA</region>
186        <code>98052</code>
187      </postal>
188      <email>paulle@microsoft.com</email>
189    </address>
190  </author>
191   
192  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
193    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
194    <address>
195      <postal>
196        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
197        <street>The Stata Center, Building 32</street>
198        <street>32 Vassar Street</street>
199        <city>Cambridge</city>
200        <region>MA</region>
201        <code>02139</code>
202        <country>USA</country>
203      </postal>
204      <email>timbl@w3.org</email>
205      <uri>http://www.w3.org/People/Berners-Lee/</uri>
206    </address>
207  </author>
208
209  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
210    <organization abbrev="W3C">World Wide Web Consortium</organization>
211    <address>
212      <postal>
213        <street>W3C / ERCIM</street>
214        <street>2004, rte des Lucioles</street>
215        <city>Sophia-Antipolis</city>
216        <region>AM</region>
217        <code>06902</code>
218        <country>France</country>
219      </postal>
220      <email>ylafon@w3.org</email>
221      <uri>http://www.raubacapeu.net/people/yves/</uri>
222    </address>
223  </author>
224
225  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
226    <organization abbrev="greenbytes">greenbytes GmbH</organization>
227    <address>
228      <postal>
229        <street>Hafenweg 16</street>
230        <city>Muenster</city><region>NW</region><code>48155</code>
231        <country>Germany</country>
232      </postal>
233      <phone>+49 251 2807760</phone>
234      <facsimile>+49 251 2807761</facsimile>
235      <email>julian.reschke@greenbytes.de</email>
236      <uri>http://greenbytes.de/tech/webdav/</uri>
237    </address>
238  </author>
239
240  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
241  <workgroup>HTTPbis Working Group</workgroup>
242
243<abstract>
244<t>
245   The Hypertext Transfer Protocol (HTTP) is an application-level
246   protocol for distributed, collaborative, hypermedia information
247   systems. HTTP has been in use by the World Wide Web global information
248   initiative since 1990. This document is Part 2 of the seven-part specification
249   that defines the protocol referred to as "HTTP/1.1" and, taken together,
250   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
251   as expressed by request methods, request-header fields, response status codes,
252   and response-header fields.
253</t>
254</abstract>
255
256<note title="Editorial Note (To be removed by RFC Editor)">
257  <t>
258    Discussion of this draft should take place on the HTTPBIS working group
259    mailing list (ietf-http-wg@w3.org). The current issues list is
260    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
261    and related documents (including fancy diffs) can be found at
262    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
263  </t>
264  <t>
265    The changes in this draft are summarized in <xref target="changes.since.10"/>.
266  </t>
267</note>
268</front>
269<middle>
270<section title="Introduction" anchor="introduction">
271<t>
272   This document defines HTTP/1.1 request and response semantics.  Each HTTP
273   message, as defined in &messaging;, is in the form of either a request or
274   a response.  An HTTP server listens on a connection for HTTP requests and
275   responds to each request, in the order received on that connection, with
276   one or more HTTP response messages.  This document defines the commonly
277   agreed upon semantics of the HTTP uniform interface, the intentions defined
278   by each request method, and the various response messages that might be
279   expected as a result of applying that method to the target resource.
280</t>
281<t>
282   This document is currently disorganized in order to minimize the changes
283   between drafts and enable reviewers to see the smaller errata changes.
284   The next draft will reorganize the sections to better reflect the content.
285   In particular, the sections will be ordered according to the typical
286   processing of an HTTP request message (after message parsing): resource
287   mapping, general header fields, methods, request modifiers, response
288   status, and resource metadata.  The current mess reflects how widely
289   dispersed these topics and associated requirements had become in
290   <xref target="RFC2616"/>.
291</t>
292
293<section title="Requirements" anchor="intro.requirements">
294<t>
295   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
296   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
297   document are to be interpreted as described in <xref target="RFC2119"/>.
298</t>
299<t>
300   An implementation is not compliant if it fails to satisfy one or more
301   of the "MUST" or "REQUIRED" level requirements for the protocols it
302   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
303   level and all the "SHOULD" level requirements for its protocols is said
304   to be "unconditionally compliant"; one that satisfies all the "MUST"
305   level requirements but not all the "SHOULD" level requirements for its
306   protocols is said to be "conditionally compliant".
307</t>
308</section>
309
310<section title="Syntax Notation" anchor="notation">
311  <x:anchor-alias value="CR"/>
312  <x:anchor-alias value="DIGIT"/>
313  <x:anchor-alias value="LF"/>
314  <x:anchor-alias value="VCHAR"/>
315  <x:anchor-alias value="WSP"/>
316<t>
317  This specification uses the ABNF syntax defined in &notation; (which
318  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
319  <xref target="collected.abnf"/> shows the collected ABNF, with the list
320  rule expanded.
321</t>
322<t>
323  The following core rules are included by
324  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
325  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
326  DIGIT (decimal 0-9), DQUOTE (double quote),
327  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
328  OCTET (any 8-bit sequence of data), SP (space),
329  VCHAR (any visible USASCII character),
330  and WSP (whitespace).
331</t>
332
333<section title="Core Rules" anchor="core.rules">
334  <x:anchor-alias value="obs-text"/>
335  <x:anchor-alias value="quoted-string"/>
336  <x:anchor-alias value="token"/>
337  <x:anchor-alias value="OWS"/>
338  <x:anchor-alias value="RWS"/>
339<t>
340  The core rules below are defined in &basic-rules;:
341</t>
342<figure><artwork type="abnf2616">
343  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
344  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
345  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
346  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
347  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
348</artwork></figure>
349</section>
350
351<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
352  <x:anchor-alias value="absolute-URI"/>
353  <x:anchor-alias value="Accept"/>
354  <x:anchor-alias value="Accept-Charset"/>
355  <x:anchor-alias value="Accept-Encoding"/>
356  <x:anchor-alias value="Accept-Language"/>
357  <x:anchor-alias value="Accept-Ranges"/>
358  <x:anchor-alias value="Age"/>
359  <x:anchor-alias value="Authorization"/>
360  <x:anchor-alias value="comment"/>
361  <x:anchor-alias value="ETag"/>
362  <x:anchor-alias value="Host"/>
363  <x:anchor-alias value="HTTP-date"/>
364  <x:anchor-alias value="If-Match"/>
365  <x:anchor-alias value="If-Modified-Since"/>
366  <x:anchor-alias value="If-None-Match"/>
367  <x:anchor-alias value="If-Range"/>
368  <x:anchor-alias value="If-Unmodified-Since"/>
369  <x:anchor-alias value="partial-URI"/>
370  <x:anchor-alias value="product"/>
371  <x:anchor-alias value="Proxy-Authenticate"/>
372  <x:anchor-alias value="Proxy-Authorization"/>
373  <x:anchor-alias value="Range"/>
374  <x:anchor-alias value="TE"/>
375  <x:anchor-alias value="URI-reference"/>
376  <x:anchor-alias value="Vary"/>
377  <x:anchor-alias value="WWW-Authenticate"/>
378<t>
379  The ABNF rules below are defined in other parts:
380</t>
381<figure><!--Part1--><artwork type="abnf2616">
382  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
383  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
384  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
385  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
386  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
387  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
388  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
389  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
390</artwork></figure>
391<figure><!--Part3--><artwork type="abnf2616">
392  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
393  <x:ref>Accept-Charset</x:ref> =
394             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
395  <x:ref>Accept-Encoding</x:ref> =
396             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
397  <x:ref>Accept-Language</x:ref> =
398             &lt;Accept-Language, defined in &header-accept-language;&gt;
399</artwork></figure>
400<figure><!--Part4--><artwork type="abnf2616">
401  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
402  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
403  <x:ref>If-Modified-Since</x:ref> =
404             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
405  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
406  <x:ref>If-Unmodified-Since</x:ref> =
407             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
408</artwork></figure>
409<figure><!--Part5--><artwork type="abnf2616">
410  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
411  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
412  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
413</artwork></figure>
414<figure><!--Part6--><artwork type="abnf2616">
415  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
416  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
417</artwork><!--Part7--></figure>
418<figure><artwork type="abnf2616">
419  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
420  <x:ref>Proxy-Authenticate</x:ref> =
421             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
422  <x:ref>Proxy-Authorization</x:ref> =
423             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
424  <x:ref>WWW-Authenticate</x:ref> =
425             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
426</artwork></figure>
427</section>
428</section>
429</section>
430
431<section title="Method" anchor="method">
432  <x:anchor-alias value="Method"/>
433  <x:anchor-alias value="extension-method"/>
434<t>
435   The Method token indicates the method to be performed on the resource
436   identified by the effective request URI (&effective-request-uri;). The
437   method is case-sensitive.
438</t>
439<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
440  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
441                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
442                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
443                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
444                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
445                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
446                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
447                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
448                 / <x:ref>extension-method</x:ref>
449  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
450</artwork></figure>
451<t>
452   The list of methods allowed by a resource can be specified in an
453   Allow header field (<xref target="header.allow"/>). The status code of the response
454   always notifies the client whether a method is currently allowed on a
455   resource, since the set of allowed methods can change dynamically. An
456   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
457   if the method is known by the origin server but not allowed for the
458   resource, and 501 (Not Implemented) if the method is
459   unrecognized or not implemented by the origin server. The methods GET
460   and HEAD &MUST; be supported by all general-purpose servers. All other
461   methods are &OPTIONAL;; however, if the above methods are implemented,
462   they &MUST; be implemented with the same semantics as those specified
463   in <xref target="method.definitions"/>.
464</t>
465
466<section title="Method Registry" anchor="method.registry">
467<t>
468  The HTTP Method Registry defines the name space for the Method token in the
469  Request line of an HTTP request.
470</t>
471<t>
472  Registrations &MUST; include the following fields:
473  <list style="symbols">
474    <t>Method Name (see <xref target="method"/>)</t>
475    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
476    <t>Pointer to specification text</t>
477  </list>
478</t>
479<t>
480  Values to be added to this name space are subject to IETF review
481  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
482</t>
483<t>
484  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
485</t>
486</section>
487</section>
488
489<section title="Request Header Fields" anchor="request.header.fields">
490  <x:anchor-alias value="request-header"/>
491<t>
492   The request-header fields allow the client to pass additional
493   information about the request, and about the client itself, to the
494   server. These fields act as request modifiers, with semantics
495   equivalent to the parameters on a programming language method
496   invocation.
497</t>
498<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
499  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
500                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
501                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
502                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
503                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
504                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
505                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
506                 / <x:ref>Host</x:ref>                     ; &header-host;
507                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
508                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
509                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
510                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
511                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
512                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
513                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
514                 / <x:ref>Range</x:ref>                    ; &header-range;
515                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
516                 / <x:ref>TE</x:ref>                       ; &header-te;
517                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
518</artwork></figure>
519<t>
520   Request-header field names can be extended reliably only in
521   combination with a change in the protocol version. However, new or
522   experimental header fields &MAY; be given the semantics of request-header
523   fields if all parties in the communication recognize them to
524   be request-header fields.
525</t>
526</section>
527
528<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
529  <x:anchor-alias value="Reason-Phrase"/>
530  <x:anchor-alias value="Status-Code"/>
531  <x:anchor-alias value="extension-code"/>
532<t>
533   The Status-Code element is a 3-digit integer result code of the
534   attempt to understand and satisfy the request. The status codes listed
535   below are defined in <xref target="status.codes"/>, &p4-status-codes;,
536   &p5-status-codes;, and &p7-status-codes;.
537</t>
538<t>
539   The Reason-Phrase is intended to give a short
540   textual description of the Status-Code. The Status-Code is intended
541   for use by automata and the Reason-Phrase is intended for the human
542   user. The client is not required to examine or display the Reason-Phrase.
543</t>
544<t> 
545   The individual values of the numeric status codes defined for
546   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
547   presented below. The reason phrases listed here are only
548   recommendations -- they &MAY; be replaced by local equivalents without
549   affecting the protocol.
550</t>
551<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/>
552  <x:ref>Status-Code</x:ref> =
553       "100"  ; <xref target="status.100"/>: Continue
554     / "101"  ; <xref target="status.101"/>: Switching Protocols
555     / "200"  ; <xref target="status.200"/>: OK
556     / "201"  ; <xref target="status.201"/>: Created
557     / "202"  ; <xref target="status.202"/>: Accepted
558     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
559     / "204"  ; <xref target="status.204"/>: No Content
560     / "205"  ; <xref target="status.205"/>: Reset Content
561     / "206"  ; &status-206;: Partial Content
562     / "300"  ; <xref target="status.300"/>: Multiple Choices
563     / "301"  ; <xref target="status.301"/>: Moved Permanently
564     / "302"  ; <xref target="status.302"/>: Found
565     / "303"  ; <xref target="status.303"/>: See Other
566     / "304"  ; &status-304;: Not Modified
567     / "305"  ; <xref target="status.305"/>: Use Proxy
568     / "307"  ; <xref target="status.307"/>: Temporary Redirect
569     / "400"  ; <xref target="status.400"/>: Bad Request
570     / "401"  ; &status-401;: Unauthorized
571     / "402"  ; <xref target="status.402"/>: Payment Required
572     / "403"  ; <xref target="status.403"/>: Forbidden
573     / "404"  ; <xref target="status.404"/>: Not Found
574     / "405"  ; <xref target="status.405"/>: Method Not Allowed
575     / "406"  ; <xref target="status.406"/>: Not Acceptable
576     / "407"  ; &status-407;: Proxy Authentication Required
577     / "408"  ; <xref target="status.408"/>: Request Time-out
578     / "409"  ; <xref target="status.409"/>: Conflict
579     / "410"  ; <xref target="status.410"/>: Gone
580     / "411"  ; <xref target="status.411"/>: Length Required
581     / "412"  ; &status-412;: Precondition Failed
582     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
583     / "414"  ; <xref target="status.414"/>: URI Too Long
584     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
585     / "416"  ; &status-416;: Requested range not satisfiable
586     / "417"  ; <xref target="status.417"/>: Expectation Failed
587     / "500"  ; <xref target="status.500"/>: Internal Server Error
588     / "501"  ; <xref target="status.501"/>: Not Implemented
589     / "502"  ; <xref target="status.502"/>: Bad Gateway
590     / "503"  ; <xref target="status.503"/>: Service Unavailable
591     / "504"  ; <xref target="status.504"/>: Gateway Time-out
592     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
593     / <x:ref>extension-code</x:ref>
594
595  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
596  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
597</artwork></figure>
598<t>
599   HTTP status codes are extensible. HTTP applications are not required
600   to understand the meaning of all registered status codes, though such
601   understanding is obviously desirable. However, applications &MUST;
602   understand the class of any status code, as indicated by the first
603   digit, and treat any unrecognized response as being equivalent to the
604   x00 status code of that class, with the exception that an
605   unrecognized response &MUST-NOT; be cached. For example, if an
606   unrecognized status code of 431 is received by the client, it can
607   safely assume that there was something wrong with its request and
608   treat the response as if it had received a 400 status code. In such
609   cases, user agents &SHOULD; present to the user the representation enclosed
610   with the response, since that representation is likely to include human-readable
611   information which will explain the unusual status.
612</t>
613
614<section title="Status Code Registry" anchor="status.code.registry">
615<t>
616  The HTTP Status Code Registry defines the name space for the Status-Code
617  token in the Status-Line of an HTTP response.
618</t>
619<t>
620  Values to be added to this name space are subject to IETF review
621  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
622</t>
623<t>
624  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
625</t>
626</section>
627
628</section>
629
630<section title="Response Header Fields" anchor="response.header.fields">
631  <x:anchor-alias value="response-header"/>
632<t>
633   The response-header fields allow the server to pass additional
634   information about the response which cannot be placed in the Status-Line.
635   These header fields give information about the server and about
636   further access to the resource identified by the effective request URI
637   (&effective-request-uri;).
638</t>
639<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
640  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
641                  / <x:ref>Age</x:ref>                     ; &header-age;
642                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
643                  / <x:ref>ETag</x:ref>                    ; &header-etag;
644                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
645                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
646                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
647                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
648                  / <x:ref>Vary</x:ref>                    ; &header-vary;
649                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
650</artwork></figure>
651<t>
652   Response-header field names can be extended reliably only in
653   combination with a change in the protocol version. However, new or
654   experimental header fields &MAY; be given the semantics of response-header
655   fields if all parties in the communication recognize them to
656   be response-header fields.
657</t>
658</section>
659
660<section title="Representation" anchor="representation">
661<t>
662   Request and Response messages &MAY; transfer a representation if not otherwise
663   restricted by the request method or response status code. A representation
664   consists of metadata (representation header fields) and data (representation
665   body).  When a complete or partial representation is enclosed in an HTTP message,
666   it is referred to as the payload of the message. HTTP representations
667   are defined in &payload;.
668</t>
669<t>
670   A representation body is only present in a message when a message-body is
671   present, as described in &message-body;. The representation body is obtained
672   from the message-body by decoding any Transfer-Encoding that might
673   have been applied to ensure safe and proper transfer of the message.
674</t>
675
676<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
677<t>
678   It is sometimes necessary to determine an identifier for the resource
679   associated with a representation.
680</t>
681<t>
682   An HTTP request representation, when present, is always associated with an
683   anonymous (i.e., unidentified) resource.
684</t>
685<t>
686   In the common case, an HTTP response is a representation of the resource
687   located at the effective request URI (see &effective-request-uri;). However,
688   this is not always the case. To determine the URI of the resource a
689   response is associated with, the following rules are used (with the first
690   applicable one being selected):
691</t>
692<t><list style="numbers">
693   <t>If the response status code is 200 or 203 and the request method was GET,
694   the response payload is a representation of the resource identified by the effective request URI.</t>
695   <t>If the response status code is 204, 206, or 304 and the request method was GET
696   or HEAD, the response payload is a partial representation of the resource identified
697   by the effective request URI (see &caching-combining-headers;).</t>
698   <t>If the response has a Content-Location header, and that URI is the same
699   as the effective request URI, the response payload is a representation of the
700   resource identified by the effective request URI.</t>
701   <t>If the response has a Content-Location header, and that URI is not the
702   same as the effective request URI, then the response asserts that its
703   payload is a representation of the resource identified by the
704   Content-Location URI. However, such an assertion cannot be trusted unless
705   it can be verified by other means (not defined by HTTP).</t>
706   <t>Otherwise, the response is a representation of an anonymous (i.e.,
707   unidentified) resource.</t>
708</list></t>
709<t>
710  <cref anchor="TODO-req-uri">
711   The comparison function is going to have to be defined somewhere,
712   because we already need to compare URIs for things like cache invalidation.</cref>
713</t>
714</section>
715
716</section>
717
718
719<section title="Method Definitions" anchor="method.definitions">
720<t>
721   The set of common methods for HTTP/1.1 is defined below. Although
722   this set can be expanded, additional methods cannot be assumed to
723   share the same semantics for separately extended clients and servers.
724</t>
725
726<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
727
728<section title="Safe Methods" anchor="safe.methods">
729<iref item="Safe Methods" primary="true"/>
730<t>
731   Implementors should be aware that the software represents the user in
732   their interactions over the Internet, and should be careful to allow
733   the user to be aware of any actions they take which might have an
734   unexpected significance to themselves or others.
735</t>
736<t>
737   In particular, the convention has been established that the GET, HEAD,
738   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
739   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
740   This allows user agents to represent other methods, such as POST, PUT
741   and DELETE, in a special way, so that the user is made aware of the
742   fact that a possibly unsafe action is being requested.
743</t>
744<t>
745   Naturally, it is not possible to ensure that the server does not
746   generate side-effects as a result of performing a GET request; in
747   fact, some dynamic resources consider that a feature. The important
748   distinction here is that the user did not request the side-effects,
749   so therefore cannot be held accountable for them.
750</t>
751</section>
752
753<section title="Idempotent Methods" anchor="idempotent.methods">
754<iref item="Idempotent Methods" primary="true"/>
755<t>
756   Methods can also have the property of "idempotence" in that, aside
757   from error or expiration issues, the intended effect of multiple
758   identical requests is the same as for a single request.
759   The methods PUT, DELETE, and all safe methods are idempotent.
760   It is important to note that idempotence refers only to changes
761   requested by the client: a server is free to change its state due
762   to multiple requests for the purpose of tracking those requests,
763   versioning of results, etc.
764</t>
765</section>
766</section>
767
768<section title="OPTIONS" anchor="OPTIONS">
769  <rdf:Description>
770    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
771  </rdf:Description>
772  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
773  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
774<t>
775   The OPTIONS method represents a request for information about the
776   communication options available on the request/response chain
777   identified by the effective request URI. This method allows the client to
778   determine the options and/or requirements associated with a resource,
779   or the capabilities of a server, without implying a resource action
780   or initiating a resource retrieval.
781</t>
782<t>
783   Responses to this method are not cacheable.
784</t>
785<t>
786   If the OPTIONS request includes a message-body (as indicated by the
787   presence of Content-Length or Transfer-Encoding), then the media type
788   &MUST; be indicated by a Content-Type field. Although this
789   specification does not define any use for such a body, future
790   extensions to HTTP might use the OPTIONS body to make more detailed
791   queries on the server.
792</t>
793<t>
794   If the request-target is an asterisk ("*"), the OPTIONS request is
795   intended to apply to the server in general rather than to a specific
796   resource. Since a server's communication options typically depend on
797   the resource, the "*" request is only useful as a "ping" or "no-op"
798   type of method; it does nothing beyond allowing the client to test
799   the capabilities of the server. For example, this can be used to test
800   a proxy for HTTP/1.1 compliance (or lack thereof).
801</t>
802<t>
803   If the request-target is not an asterisk, the OPTIONS request applies
804   only to the options that are available when communicating with that
805   resource.
806</t>
807<t>
808   A 200 response &SHOULD; include any header fields that indicate
809   optional features implemented by the server and applicable to that
810   resource (e.g., Allow), possibly including extensions not defined by
811   this specification. The response body, if any, &SHOULD; also include
812   information about the communication options. The format for such a
813   body is not defined by this specification, but might be defined by
814   future extensions to HTTP. Content negotiation &MAY; be used to select
815   the appropriate response format. If no response body is included, the
816   response &MUST; include a Content-Length field with a field-value of
817   "0".
818</t>
819<t>
820   The Max-Forwards request-header field &MAY; be used to target a
821   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
822   If no Max-Forwards field is present in the request, then the forwarded
823   request &MUST-NOT; include a Max-Forwards field.
824</t>
825</section>
826
827<section title="GET" anchor="GET">
828  <rdf:Description>
829    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
830  </rdf:Description>
831  <iref primary="true" item="GET method" x:for-anchor=""/>
832  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
833<t>
834   The GET method means retrieve whatever information (in the form of a
835   representation) currently corresponds to the resource identified by the
836   effective request URI.
837</t>
838<t>   
839   If the effective request URI identifies a data-producing process, it is the
840   produced data which shall be returned as the representation in the response and not
841   the source text of the process, unless that text happens to be the output of
842   the process.
843</t>
844<t>
845   The semantics of the GET method change to a "conditional GET" if the
846   request message includes an If-Modified-Since, If-Unmodified-Since,
847   If-Match, If-None-Match, or If-Range header field. A conditional GET
848   method requests that the representation be transferred only under the
849   circumstances described by the conditional header field(s). The
850   conditional GET method is intended to reduce unnecessary network
851   usage by allowing cached representations to be refreshed without requiring
852   multiple requests or transferring data already held by the client.
853</t>
854<t>
855   The semantics of the GET method change to a "partial GET" if the
856   request message includes a Range header field. A partial GET requests
857   that only part of the representation be transferred, as described in &header-range;.
858   The partial GET method is intended to reduce unnecessary
859   network usage by allowing partially-retrieved representations to be
860   completed without transferring data already held by the client.
861</t>
862<t>
863   The response to a GET request is cacheable and &MAY; be used to satisfy
864   subsequent GET and HEAD requests (see &caching;).
865</t>
866<t>
867   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
868</t>
869</section>
870
871<section title="HEAD" anchor="HEAD">
872  <rdf:Description>
873    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
874  </rdf:Description>
875  <iref primary="true" item="HEAD method" x:for-anchor=""/>
876  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
877<t>
878   The HEAD method is identical to GET except that the server &MUST-NOT;
879   return a message-body in the response. The metadata contained
880   in the HTTP headers in response to a HEAD request &SHOULD; be identical
881   to the information sent in response to a GET request. This method can
882   be used for obtaining metadata about the representation implied by the
883   request without transferring the representation body. This method is
884   often used for testing hypertext links for validity, accessibility,
885   and recent modification.
886</t>
887<t>
888   The response to a HEAD request is cacheable and &MAY; be used to satisfy
889   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
890   representation from that resource; if the new field values
891   indicate that the cached representation differs from the current representation (as
892   would be indicated by a change in Content-Length, Content-MD5, ETag
893   or Last-Modified), then the cache &MUST; treat the cache entry as
894   stale.
895</t>
896</section>
897
898<section title="POST" anchor="POST">
899  <iref primary="true" item="POST method" x:for-anchor=""/>
900  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
901<t>
902   The POST method is used to request that the origin server accept the
903   representation enclosed in the request as data to be processed by the resource
904   identified by the effective request URI. POST is designed
905   to allow a uniform method to cover the following functions:
906  <list style="symbols">
907    <t>
908      Annotation of existing resources;
909    </t>
910    <t>
911        Posting a message to a bulletin board, newsgroup, mailing list,
912        or similar group of articles;
913    </t>
914    <t>
915        Providing a block of data, such as the result of submitting a
916        form, to a data-handling process;
917    </t>
918    <t>
919        Extending a database through an append operation.
920    </t>
921  </list>
922</t>
923<t>
924   The actual function performed by the POST method is determined by the
925   server and is usually dependent on the effective request URI.
926</t>
927<t>
928   The action performed by the POST method might not result in a
929   resource that can be identified by a URI. In this case, either 200
930   (OK) or 204 (No Content) is the appropriate response status code,
931   depending on whether or not the response includes a representation that
932   describes the result.
933</t>
934<t>
935   If a resource has been created on the origin server, the response
936   &SHOULD; be 201 (Created) and contain a representation which describes the
937   status of the request and refers to the new resource, and a Location
938   header (see <xref target="header.location"/>).
939</t>
940<t>
941   Responses to POST requests are only cacheable when they
942   include explicit freshness information (see &p6-explicit;). A
943   cached POST response with a Content-Location header
944   (see &header-content-location;) whose value is the Effective
945   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
946</t>
947<t>
948   Note that POST caching is not widely implemented.
949   However, the 303 (See Other) response can be used to direct the
950   user agent to retrieve a cacheable resource.
951</t>
952</section>
953
954<section title="PUT" anchor="PUT">
955  <iref primary="true" item="PUT method" x:for-anchor=""/>
956  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
957<t>
958   The PUT method requests that the enclosed representation be stored at the
959   effective request URI. If the effective request URI refers to an already
960   existing resource, the enclosed representation &SHOULD; be considered a
961   modified version of the one residing on the origin server. Otherwise, if the
962   effective request URI does not point to an existing resource, and that URI is
963   capable of being defined as a new resource by the requesting user
964   agent, the origin server can create the resource with that URI.
965</t>
966<t>   
967   If a new resource is created at the effective request URI, the origin
968   server &MUST; inform the user agent
969   via the 201 (Created) response. If an existing resource is modified,
970   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
971   to indicate successful completion of the request.
972</t>
973<t>   
974   If the resource identified by the effective request URI could not be
975   created or modified, an appropriate error response &SHOULD; be given
976   that reflects the nature of the problem.
977   The recipient of the representation &MUST-NOT; ignore any Content-*
978   headers (headers starting with the prefix "Content-") that it does
979   not understand or implement
980   and &MUST; return a 501 (Not Implemented) response in such cases.
981</t>
982<t>
983   If the request passes through a cache that has one or more stored
984   responses for the effective request URI, those stored responses
985   &SHOULD; be marked as stale if the response to the PUT request
986   has a success status code. Responses to the PUT method are
987   not cacheable.
988</t>
989<t>
990   The fundamental difference between the POST and PUT requests is
991   reflected in the different meaning of the effective request URI. The URI in a
992   POST request identifies the resource that will handle the enclosed
993   representation. That resource might be a data-accepting process, a gateway to
994   some other protocol, or a document that accepts annotations.
995   In contrast, the URI in a PUT request identifies the resource for
996   which enclosed representation is a new or replacement value; the
997   user agent knows what URI is intended and the server &MUST-NOT; attempt
998   to apply the request to some other resource.
999   If the server desires that the request be applied to a different URI,
1000   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1001   then make its own decision regarding whether or not to redirect the
1002   request.
1003</t>
1004<t>
1005   A single resource &MAY; be identified by many different URIs. For
1006   example, an article might have a URI for identifying "the current
1007   version" which is separate from the URI identifying each particular
1008   version. In this case, a PUT request on a general URI might result in
1009   several other URIs being defined by the origin server.
1010</t>
1011<t>
1012   HTTP/1.1 does not define how a PUT method affects the state of an
1013   origin server.
1014</t>
1015<t>
1016   Header fields in a PUT request that are recognized as representation
1017   metadata &SHOULD; be applied to the resource created or modified by
1018   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1019</t>
1020</section>
1021
1022<section title="DELETE" anchor="DELETE">
1023  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1024  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1025<t>
1026   The DELETE method requests that the origin server delete the resource
1027   identified by the effective request URI. This method &MAY; be overridden by
1028   human intervention (or other means) on the origin server. The client cannot
1029   be guaranteed that the operation has been carried out, even if the
1030   status code returned from the origin server indicates that the action
1031   has been completed successfully. However, the server &SHOULD-NOT; 
1032   indicate success unless, at the time the response is given, it
1033   intends to delete the resource or move it to an inaccessible
1034   location.
1035</t>
1036<t>
1037   A successful response &SHOULD; be 200 (OK) if the response includes an
1038   representation describing the status, 202 (Accepted) if the action has not
1039   yet been enacted, or 204 (No Content) if the action has been enacted
1040   but the response does not include a representation.
1041</t>
1042<t>
1043   If the request passes through a cache and the effective request URI
1044   identifies one or more currently cached representations, those entries &SHOULD; be
1045   treated as stale. Responses to the DELETE method are not cacheable.
1046</t>
1047</section>
1048
1049<section title="TRACE" anchor="TRACE">
1050  <rdf:Description>
1051    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1052  </rdf:Description>
1053  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1054  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1055<t>
1056   The TRACE method is used to invoke a remote, application-layer loop-back
1057   of the request message. The final recipient of the request
1058   &SHOULD; reflect the message received back to the client as the
1059   message-body of a 200 (OK) response. The final recipient is either the
1060   origin server or the first proxy or gateway to receive a Max-Forwards
1061   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1062   A TRACE request &MUST-NOT; include a message-body.
1063</t>
1064<t>
1065   TRACE allows the client to see what is being received at the other
1066   end of the request chain and use that data for testing or diagnostic
1067   information. The value of the Via header field (&header-via;) is of
1068   particular interest, since it acts as a trace of the request chain.
1069   Use of the Max-Forwards header field allows the client to limit the
1070   length of the request chain, which is useful for testing a chain of
1071   proxies forwarding messages in an infinite loop.
1072</t>
1073<t>
1074   If the request is valid, the response &SHOULD; have a Content-Type of
1075   "message/http" (see &media-type-message-http;) and contain a message-body
1076   that encloses a copy of the entire request message.
1077   Responses to the TRACE method are not cacheable.
1078</t>
1079</section>
1080
1081<section title="CONNECT" anchor="CONNECT">
1082  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1083  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1084<t>
1085   This specification reserves the method name CONNECT for use with a
1086   proxy that can dynamically switch to being a tunnel (e.g., SSL
1087   tunneling <xref target="RFC2817"/>).
1088</t>
1089</section>
1090</section>
1091
1092
1093<section title="Status Code Definitions" anchor="status.codes">
1094<t>
1095   Each Status-Code is described below, including any metadata required
1096   in the response.
1097</t>
1098
1099<section title="Informational 1xx" anchor="status.1xx">
1100<t>
1101   This class of status code indicates a provisional response,
1102   consisting only of the Status-Line and optional headers, and is
1103   terminated by an empty line. There are no required headers for this
1104   class of status code. Since HTTP/1.0 did not define any 1xx status
1105   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1106   except under experimental conditions.
1107</t>
1108<t>
1109   A client &MUST; be prepared to accept one or more 1xx status responses
1110   prior to a regular response, even if the client does not expect a 100
1111   (Continue) status message. Unexpected 1xx status responses &MAY; be
1112   ignored by a user agent.
1113</t>
1114<t>
1115   Proxies &MUST; forward 1xx responses, unless the connection between the
1116   proxy and its client has been closed, or unless the proxy itself
1117   requested the generation of the 1xx response. (For example, if a
1118   proxy adds a "Expect: 100-continue" field when it forwards a request,
1119   then it need not forward the corresponding 100 (Continue)
1120   response(s).)
1121</t>
1122
1123<section title="100 Continue" anchor="status.100">
1124  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1125  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1126<t>
1127   The client &SHOULD; continue with its request. This interim response is
1128   used to inform the client that the initial part of the request has
1129   been received and has not yet been rejected by the server. The client
1130   &SHOULD; continue by sending the remainder of the request or, if the
1131   request has already been completed, ignore this response. The server
1132   &MUST; send a final response after the request has been completed. See
1133   &use100; for detailed discussion of the use and handling of this
1134   status code.
1135</t>
1136</section>
1137
1138<section title="101 Switching Protocols" anchor="status.101">
1139  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1140  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1141<t>
1142   The server understands and is willing to comply with the client's
1143   request, via the Upgrade message header field (&header-upgrade;), for a
1144   change in the application protocol being used on this connection. The
1145   server will switch protocols to those defined by the response's
1146   Upgrade header field immediately after the empty line which
1147   terminates the 101 response.
1148</t>
1149<t>
1150   The protocol &SHOULD; be switched only when it is advantageous to do
1151   so. For example, switching to a newer version of HTTP is advantageous
1152   over older versions, and switching to a real-time, synchronous
1153   protocol might be advantageous when delivering resources that use
1154   such features.
1155</t>
1156</section>
1157</section>
1158
1159<section title="Successful 2xx" anchor="status.2xx">
1160<t>
1161   This class of status code indicates that the client's request was
1162   successfully received, understood, and accepted.
1163</t>
1164
1165<section title="200 OK" anchor="status.200">
1166  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1167  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1168<t>
1169   The request has succeeded. The payload returned with the response
1170   is dependent on the method used in the request, for example:
1171  <list style="hanging">
1172    <t hangText="GET">
1173          a representation of the resource corresponding to the effective
1174          request URI is sent in the response;
1175    </t>
1176    <t hangText="HEAD">
1177          the same representation as GET, except without the message-body;
1178    </t>
1179    <t hangText="POST">
1180      a representation describing or containing the result of the action;
1181    </t>
1182    <t hangText="TRACE">
1183      a representation containing the request message as received by the
1184      end server.
1185    </t>
1186  </list>
1187</t>
1188<t>
1189   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1190   freshness for 200 responses.
1191</t>
1192</section>
1193
1194<section title="201 Created" anchor="status.201">
1195  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1196  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1197<t>
1198   The request has been fulfilled and has resulted in a new resource being
1199   created. The newly created resource can be referenced by the URI(s)
1200   returned in the payload of the response, with the most specific URI
1201   for the resource given by a Location header field. The response
1202   &SHOULD; include a payload containing a list of resource
1203   characteristics and location(s) from which the user or user agent can
1204   choose the one most appropriate. The payload format is specified by
1205   the media type given in the Content-Type header field. The origin
1206   server &MUST; create the resource before returning the 201 status code.
1207   If the action cannot be carried out immediately, the server &SHOULD;
1208   respond with 202 (Accepted) response instead.
1209</t>
1210<t>
1211   A 201 response &MAY; contain an ETag response header field indicating
1212   the current value of the entity-tag for the representation of the resource
1213   just created (see &header-etag;).
1214</t>
1215</section>
1216
1217<section title="202 Accepted" anchor="status.202">
1218  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1219  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1220<t>
1221   The request has been accepted for processing, but the processing has
1222   not been completed.  The request might or might not eventually be
1223   acted upon, as it might be disallowed when processing actually takes
1224   place. There is no facility for re-sending a status code from an
1225   asynchronous operation such as this.
1226</t>
1227<t>
1228   The 202 response is intentionally non-committal. Its purpose is to
1229   allow a server to accept a request for some other process (perhaps a
1230   batch-oriented process that is only run once per day) without
1231   requiring that the user agent's connection to the server persist
1232   until the process is completed. The representation returned with this
1233   response &SHOULD; include an indication of the request's current status
1234   and either a pointer to a status monitor or some estimate of when the
1235   user can expect the request to be fulfilled.
1236</t>
1237</section>
1238
1239<section title="203 Non-Authoritative Information" anchor="status.203">
1240  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1241  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1242<t>
1243   The returned metadata in the header fields is not the
1244   definitive set as available from the origin server, but is gathered
1245   from a local or a third-party copy. The set presented &MAY; be a subset
1246   or superset of the original version. For example, including local
1247   annotation information about the resource might result in a superset
1248   of the metadata known by the origin server. Use of this
1249   response code is not required and is only appropriate when the
1250   response would otherwise be 200 (OK).
1251</t>
1252<t>
1253   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1254   freshness for 203 responses.
1255</t>
1256
1257</section>
1258
1259<section title="204 No Content" anchor="status.204">
1260  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1261  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1262<t>
1263   The server has successfully fulfilled the request, but there is no
1264   additional content to return in the response payload body.  The
1265   resource metadata and representation metadata in the response message's
1266   header fields refer to the target resource
1267   and its current representation, respectively, after the requested action.
1268   For example, if a 204 status code is received in response to a PUT
1269   and the response contains an ETag header field, then the value of
1270   that field is the current entity-tag for the representation that
1271   was successfully PUT.
1272</t>
1273<t>
1274   If the client is a user agent, it &SHOULD-NOT; change its document view
1275   from that which caused the request to be sent. This response is
1276   primarily intended to allow input for actions to take place without
1277   causing a change to the user agent's active document view, although
1278   any new or updated metadata &SHOULD; be applied to the document
1279   currently in the user agent's active view.
1280</t>
1281<t>
1282   The 204 response &MUST-NOT; include a message-body, and thus is always
1283   terminated by the first empty line after the header fields.
1284</t>
1285</section>
1286
1287<section title="205 Reset Content" anchor="status.205">
1288  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1289  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1290<t>
1291   The server has fulfilled the request and the user agent &SHOULD; reset
1292   the document view which caused the request to be sent. This response
1293   is primarily intended to allow input for actions to take place via
1294   user input, followed by a clearing of the form in which the input is
1295   given so that the user can easily initiate another input action. The
1296   response &MUST-NOT; include a message-body.
1297</t>
1298</section>
1299
1300<section title="206 Partial Content" anchor="status.206">
1301  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1302  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1303  <rdf:Description>
1304    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1305  </rdf:Description>
1306<t>
1307   The server has fulfilled the partial GET request for the resource
1308   and the enclosed payload is a partial representation as defined in &status-206;.
1309</t>
1310<t>
1311   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1312   freshness for 206 responses.
1313</t>
1314</section>
1315</section>
1316
1317<section title="Redirection 3xx" anchor="status.3xx">
1318<t>
1319   This class of status code indicates that further action needs to be
1320   taken by the user agent in order to fulfill the request.  The action
1321   required &MAY; be carried out by the user agent without interaction
1322   with the user if and only if the method used in the second request is
1323   known to be "safe", as defined in <xref target="safe.methods"/>.
1324   A client &SHOULD; detect infinite redirection loops, since such loops
1325   generate network traffic for each redirection.
1326</t>
1327<x:note>
1328  <t>
1329    <x:h>Note:</x:h> An earlier version of this specification recommended a
1330    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1331    Content developers should be aware that there might be clients that
1332    implement such a fixed limitation.
1333  </t>
1334</x:note>
1335
1336<section title="300 Multiple Choices" anchor="status.300">
1337  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1338  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1339<t>
1340   The target resource more than one
1341   representation, each with its own specific location, and agent-driven
1342   negotiation information (&content-negotiation;) is being provided so that
1343   the user (or user agent) can select a preferred representation by
1344   redirecting its request to that location.
1345</t>
1346<t>
1347   Unless it was a HEAD request, the response &SHOULD; include a representation
1348   containing a list of representation metadata and location(s) from
1349   which the user or user agent can choose the one most appropriate. The
1350   data format is specified by the media type given in the Content-Type
1351   header field. Depending upon the format and the capabilities of
1352   the user agent, selection of the most appropriate choice &MAY; be
1353   performed automatically. However, this specification does not define
1354   any standard for such automatic selection.
1355</t>
1356<t>
1357   If the server has a preferred choice of representation, it &SHOULD;
1358   include the specific URI for that representation in the Location
1359   field; user agents &MAY; use the Location field value for automatic
1360   redirection.
1361</t>
1362<t>
1363   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1364   freshness for 300 responses.
1365</t>
1366
1367</section>
1368
1369<section title="301 Moved Permanently" anchor="status.301">
1370  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1371  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1372<t>
1373   The target resource has been assigned a new permanent URI and any
1374   future references to this resource &SHOULD; use one of the returned
1375   URIs.  Clients with link editing capabilities ought to automatically
1376   re-link references to the effective request URI to one or more of the new
1377   references returned by the server, where possible.
1378</t>
1379<t>
1380   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1381   freshness for 301 responses.
1382</t>
1383<t>
1384   The new permanent URI &SHOULD; be given by the Location field in the
1385   response. Unless the request method was HEAD, the representation of the
1386   response &SHOULD; contain a short hypertext note with a hyperlink to
1387   the new URI(s).
1388</t>
1389<t>
1390   If the 301 status code is received in response to a request method
1391   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1392   then the request &MAY; be automatically redirected by the user agent without
1393   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1394   request unless it can be confirmed by the user, since this might
1395   change the conditions under which the request was issued.
1396</t>
1397<x:note>
1398  <t>
1399    <x:h>Note:</x:h> When automatically redirecting a POST request after
1400    receiving a 301 status code, some existing HTTP/1.0 user agents
1401    will erroneously change it into a GET request.
1402  </t>
1403</x:note>
1404</section>
1405
1406<section title="302 Found" anchor="status.302">
1407  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1408  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1409<t>
1410   The target resource resides temporarily under a different URI.
1411   Since the redirection might be altered on occasion, the client &SHOULD;
1412   continue to use the effective request URI for future requests.
1413</t>
1414<t>
1415   The temporary URI &SHOULD; be given by the Location field in the
1416   response. Unless the request method was HEAD, the representation of the
1417   response &SHOULD; contain a short hypertext note with a hyperlink to
1418   the new URI(s).
1419</t>
1420<t>
1421   If the 302 status code is received in response to a request method
1422   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1423   then the request &MAY; be automatically redirected by the user agent without
1424   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1425   request unless it can be confirmed by the user, since this might
1426   change the conditions under which the request was issued.
1427</t>
1428<x:note>
1429  <t>
1430    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1431    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1432    specify that the client is not allowed to change the method on the
1433    redirected request.  However, most existing user agent implementations
1434    treat 302 as if it were a 303 response, performing a GET on the Location
1435    field-value regardless of the original request method. Therefore, a
1436    previous version of this specification
1437    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1438    status codes
1439    <xref target="status.303" format="none">303</xref> and
1440    <xref target="status.307" format="none">307</xref> for servers that wish
1441    to make unambiguously clear which kind of reaction is expected of the
1442    client.
1443  </t>
1444</x:note>
1445</section>
1446
1447<section title="303 See Other" anchor="status.303">
1448  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1449  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1450<t>
1451   The server directs the user agent to a different resource, indicated
1452   by a URI in the Location header field, that provides an indirect
1453   response to the original request.  The user agent &MAY; perform a GET
1454   request on the URI in the Location field in order to obtain a
1455   representation corresponding to the response, be redirected again,
1456   or end with an error status.  The Location URI is not a substitute
1457   reference for the effective request URI.
1458</t>
1459<t>
1460   The 303 status code is generally applicable to any HTTP method.  It is
1461   primarily used to allow the output of a POST action to redirect
1462   the user agent to a selected resource, since doing so provides the
1463   information corresponding to the POST response in a form that
1464   can be separately identified, bookmarked, and cached independent
1465   of the original request.
1466</t>
1467<t>
1468   A 303 response to a GET request indicates that the requested
1469   resource does not have a representation of its own that can be
1470   transferred by the server over HTTP.  The Location URI indicates a
1471   resource that is descriptive of the target resource, such that the
1472   follow-on representation might be useful to recipients without
1473   implying that it adequately represents the target resource.
1474   Note that answers to the questions of what can be represented, what
1475   representations are adequate, and what might be a useful description
1476   are outside the scope of HTTP and thus entirely determined by the
1477   URI owner(s).
1478</t>
1479<t>
1480   Except for responses to a HEAD request, the representation of a 303
1481   response &SHOULD; contain a short hypertext note with a hyperlink
1482   to the Location URI.
1483</t>
1484</section>
1485
1486<section title="304 Not Modified" anchor="status.304">
1487  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1488  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1489  <rdf:Description>
1490    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1491  </rdf:Description>
1492<t>
1493   The response to the request has not been modified since the conditions
1494   indicated by the client's conditional GET request, as defined in &status-304;.
1495</t>
1496</section>
1497
1498<section title="305 Use Proxy" anchor="status.305">
1499  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1500  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1501<t>
1502   The 305 status code was defined in a previous version of this specification
1503   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1504</t>
1505</section>
1506
1507<section title="306 (Unused)" anchor="status.306">
1508  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1509  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1510<t>
1511   The 306 status code was used in a previous version of the
1512   specification, is no longer used, and the code is reserved.
1513</t>
1514</section>
1515
1516<section title="307 Temporary Redirect" anchor="status.307">
1517  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1518  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1519<t>
1520   The target resource resides temporarily under a different URI.
1521   Since the redirection can change over time, the client &SHOULD;
1522   continue to use the effective request URI for future requests.
1523</t>
1524<t>
1525   The temporary URI &SHOULD; be given by the Location field in the
1526   response. Unless the request method was HEAD, the representation of the
1527   response &SHOULD; contain a short hypertext note with a hyperlink to
1528   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1529   understand the 307 status code. Therefore, the note &SHOULD; contain the
1530   information necessary for a user to repeat the original request on
1531   the new URI.
1532</t>
1533<t>
1534   If the 307 status code is received in response to a request method
1535   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1536   then the request &MAY; be automatically redirected by the user agent without
1537   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1538   request unless it can be confirmed by the user, since this might
1539   change the conditions under which the request was issued.
1540</t>
1541</section>
1542</section>
1543
1544<section title="Client Error 4xx" anchor="status.4xx">
1545<t>
1546   The 4xx class of status code is intended for cases in which the
1547   client seems to have erred. Except when responding to a HEAD request,
1548   the server &SHOULD; include a representation containing an explanation of the
1549   error situation, and whether it is a temporary or permanent
1550   condition. These status codes are applicable to any request method.
1551   User agents &SHOULD; display any included representation to the user.
1552</t>
1553<t>
1554   If the client is sending data, a server implementation using TCP
1555   &SHOULD; be careful to ensure that the client acknowledges receipt of
1556   the packet(s) containing the response, before the server closes the
1557   input connection. If the client continues sending data to the server
1558   after the close, the server's TCP stack will send a reset packet to
1559   the client, which might erase the client's unacknowledged input buffers
1560   before they can be read and interpreted by the HTTP application.
1561</t>
1562
1563<section title="400 Bad Request" anchor="status.400">
1564  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1565  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1566<t>
1567   The request could not be understood by the server due to malformed
1568   syntax. The client &SHOULD-NOT; repeat the request without
1569   modifications.
1570</t>
1571</section>
1572
1573<section title="401 Unauthorized" anchor="status.401">
1574  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1575  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1576  <rdf:Description>
1577    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1578  </rdf:Description>
1579<t>
1580   The request requires user authentication (see &status-401;).
1581</t>
1582</section>
1583
1584<section title="402 Payment Required" anchor="status.402">
1585  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1586  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1587<t>
1588   This code is reserved for future use.
1589</t>
1590</section>
1591
1592<section title="403 Forbidden" anchor="status.403">
1593  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1594  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1595<t>
1596   The server understood the request, but is refusing to fulfill it.
1597   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1598   If the request method was not HEAD and the server wishes to make
1599   public why the request has not been fulfilled, it &SHOULD; describe the
1600   reason for the refusal in the representation.  If the server does not wish to
1601   make this information available to the client, the status code 404
1602   (Not Found) can be used instead.
1603</t>
1604</section>
1605
1606<section title="404 Not Found" anchor="status.404">
1607  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1608  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1609<t>
1610   The server has not found anything matching the effective request URI. No
1611   indication is given of whether the condition is temporary or
1612   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1613   knows, through some internally configurable mechanism, that an old
1614   resource is permanently unavailable and has no forwarding address.
1615   This status code is commonly used when the server does not wish to
1616   reveal exactly why the request has been refused, or when no other
1617   response is applicable.
1618</t>
1619</section>
1620
1621<section title="405 Method Not Allowed" anchor="status.405">
1622  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1623  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1624<t>
1625   The method specified in the Request-Line is not allowed for the target
1626   resource. The response &MUST; include an
1627   Allow header containing a list of valid methods for the requested
1628   resource.
1629</t>
1630</section>
1631
1632<section title="406 Not Acceptable" anchor="status.406">
1633  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1634  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1635<t>
1636   The resource identified by the request is only capable of generating
1637   response representations which have content characteristics not acceptable
1638   according to the accept headers sent in the request.
1639</t>
1640<t>
1641   Unless it was a HEAD request, the response &SHOULD; include a representation
1642   containing a list of available representation characteristics and location(s)
1643   from which the user or user agent can choose the one most
1644   appropriate. The data format is specified by the media type given
1645   in the Content-Type header field. Depending upon the format and the
1646   capabilities of the user agent, selection of the most appropriate
1647   choice &MAY; be performed automatically. However, this specification
1648   does not define any standard for such automatic selection.
1649</t>
1650<x:note>
1651  <t>
1652    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1653    not acceptable according to the accept headers sent in the
1654    request. In some cases, this might even be preferable to sending a
1655    406 response. User agents are encouraged to inspect the headers of
1656    an incoming response to determine if it is acceptable.
1657  </t>
1658</x:note>
1659<t>
1660   If the response could be unacceptable, a user agent &SHOULD;
1661   temporarily stop receipt of more data and query the user for a
1662   decision on further actions.
1663</t>
1664</section>
1665
1666<section title="407 Proxy Authentication Required" anchor="status.407">
1667  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1668  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1669<t>
1670   This code is similar to 401 (Unauthorized), but indicates that the
1671   client must first authenticate itself with the proxy (see &status-407;).
1672</t>
1673</section>
1674
1675<section title="408 Request Timeout" anchor="status.408">
1676  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1677  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1678<t>
1679   The client did not produce a request within the time that the server
1680   was prepared to wait. The client &MAY; repeat the request without
1681   modifications at any later time.
1682</t>
1683</section>
1684
1685<section title="409 Conflict" anchor="status.409">
1686  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1687  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1688<t>
1689   The request could not be completed due to a conflict with the current
1690   state of the resource. This code is only allowed in situations where
1691   it is expected that the user might be able to resolve the conflict
1692   and resubmit the request. The response body &SHOULD; include enough
1693   information for the user to recognize the source of the conflict.
1694   Ideally, the response representation would include enough information for the
1695   user or user agent to fix the problem; however, that might not be
1696   possible and is not required.
1697</t>
1698<t>
1699   Conflicts are most likely to occur in response to a PUT request. For
1700   example, if versioning were being used and the representation being PUT
1701   included changes to a resource which conflict with those made by an
1702   earlier (third-party) request, the server might use the 409 response
1703   to indicate that it can't complete the request. In this case, the
1704   response representation would likely contain a list of the differences
1705   between the two versions in a format defined by the response
1706   Content-Type.
1707</t>
1708</section>
1709
1710<section title="410 Gone" anchor="status.410">
1711  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1712  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1713<t>
1714   The target resource is no longer available at the server and no
1715   forwarding address is known. This condition is expected to be
1716   considered permanent. Clients with link editing capabilities &SHOULD;
1717   delete references to the effective request URI after user approval. If the
1718   server does not know, or has no facility to determine, whether or not
1719   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1720   used instead.
1721</t>
1722<t>
1723   The 410 response is primarily intended to assist the task of web
1724   maintenance by notifying the recipient that the resource is
1725   intentionally unavailable and that the server owners desire that
1726   remote links to that resource be removed. Such an event is common for
1727   limited-time, promotional services and for resources belonging to
1728   individuals no longer working at the server's site. It is not
1729   necessary to mark all permanently unavailable resources as "gone" or
1730   to keep the mark for any length of time -- that is left to the
1731   discretion of the server owner.
1732</t>
1733<t>
1734   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1735   for 410 responses.
1736</t>
1737
1738</section>
1739
1740<section title="411 Length Required" anchor="status.411">
1741  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1742  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1743<t>
1744   The server refuses to accept the request without a defined Content-Length.
1745   The client &MAY; repeat the request if it adds a valid
1746   Content-Length header field containing the length of the message-body
1747   in the request message.
1748</t>
1749</section>
1750
1751<section title="412 Precondition Failed" anchor="status.412">
1752  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1753  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1754  <rdf:Description>
1755    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1756  </rdf:Description>
1757<t>
1758   The precondition given in one or more of the request-header fields
1759   evaluated to false when it was tested on the server, as defined in
1760   &status-412;.
1761</t>
1762</section>
1763
1764<section title="413 Request Entity Too Large" anchor="status.413">
1765  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1766  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1767<t>
1768   The server is refusing to process a request because the request
1769   representation is larger than the server is willing or able to process. The
1770   server &MAY; close the connection to prevent the client from continuing
1771   the request.
1772</t>
1773<t>
1774   If the condition is temporary, the server &SHOULD; include a Retry-After
1775   header field to indicate that it is temporary and after what
1776   time the client &MAY; try again.
1777</t>
1778</section>
1779
1780<section title="414 URI Too Long" anchor="status.414">
1781  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1782  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1783<t>
1784   The server is refusing to service the request because the effective request URI
1785   is longer than the server is willing to interpret. This rare
1786   condition is only likely to occur when a client has improperly
1787   converted a POST request to a GET request with long query
1788   information, when the client has descended into a URI "black hole" of
1789   redirection (e.g., a redirected URI prefix that points to a suffix of
1790   itself), or when the server is under attack by a client attempting to
1791   exploit security holes present in some servers using fixed-length
1792   buffers for reading or manipulating the effective request URI.
1793</t>
1794</section>
1795
1796<section title="415 Unsupported Media Type" anchor="status.415">
1797  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1798  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1799<t>
1800   The server is refusing to service the request because the representation of
1801   the request is in a format not supported by the target resource
1802   for the requested method.
1803</t>
1804</section>
1805
1806<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1807  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1808  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1809  <rdf:Description>
1810    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1811  </rdf:Description>
1812<t>
1813   The request included a Range request-header field (&header-range;) and none of
1814   the range-specifier values in this field overlap the current extent
1815   of the selected resource. See &status-416;.
1816</t>
1817</section>
1818
1819<section title="417 Expectation Failed" anchor="status.417">
1820  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1821  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1822<t>
1823   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1824   could not be met by this server, or, if the server is a proxy,
1825   the server has unambiguous evidence that the request could not be met
1826   by the next-hop server.
1827</t>
1828</section>
1829</section>
1830
1831<section title="Server Error 5xx" anchor="status.5xx">
1832<t>
1833   Response status codes beginning with the digit "5" indicate cases in
1834   which the server is aware that it has erred or is incapable of
1835   performing the request. Except when responding to a HEAD request, the
1836   server &SHOULD; include a representation containing an explanation of the
1837   error situation, and whether it is a temporary or permanent
1838   condition. User agents &SHOULD; display any included representation to the
1839   user. These response codes are applicable to any request method.
1840</t>
1841
1842<section title="500 Internal Server Error" anchor="status.500">
1843  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1844  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1845<t>
1846   The server encountered an unexpected condition which prevented it
1847   from fulfilling the request.
1848</t>
1849</section>
1850
1851<section title="501 Not Implemented" anchor="status.501">
1852  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1853  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1854<t>
1855   The server does not support the functionality required to fulfill the
1856   request. This is the appropriate response when the server does not
1857   recognize the request method and is not capable of supporting it for
1858   any resource.
1859</t>
1860</section>
1861
1862<section title="502 Bad Gateway" anchor="status.502">
1863  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1864  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1865<t>
1866   The server, while acting as a gateway or proxy, received an invalid
1867   response from the upstream server it accessed in attempting to
1868   fulfill the request.
1869</t>
1870</section>
1871
1872<section title="503 Service Unavailable" anchor="status.503">
1873  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1874  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1875<t>
1876   The server is currently unable to handle the request due to a
1877   temporary overloading or maintenance of the server. The implication
1878   is that this is a temporary condition which will be alleviated after
1879   some delay. If known, the length of the delay &MAY; be indicated in a
1880   Retry-After header. If no Retry-After is given, the client &SHOULD;
1881   handle the response as it would for a 500 response.
1882</t>
1883<x:note>
1884  <t>
1885    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1886    server must use it when becoming overloaded. Some servers might wish
1887    to simply refuse the connection.
1888  </t>
1889</x:note>
1890</section>
1891
1892<section title="504 Gateway Timeout" anchor="status.504">
1893  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1894  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1895<t>
1896   The server, while acting as a gateway or proxy, did not receive a
1897   timely response from the upstream server specified by the URI (e.g.,
1898   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1899   to access in attempting to complete the request.
1900</t>
1901<x:note>
1902  <t>
1903    <x:h>Note</x:h> to implementors: some deployed proxies are known to
1904    return 400 or 500 when DNS lookups time out.
1905  </t>
1906</x:note>
1907</section>
1908
1909<section title="505 HTTP Version Not Supported" anchor="status.505">
1910  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1911  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1912<t>
1913   The server does not support, or refuses to support, the protocol
1914   version that was used in the request message. The server is
1915   indicating that it is unable or unwilling to complete the request
1916   using the same major version as the client, as described in &http-version;,
1917   other than with this error message. The response &SHOULD; contain
1918   a representation describing why that version is not supported and what other
1919   protocols are supported by that server.
1920</t>
1921
1922</section>
1923</section>
1924</section>
1925
1926
1927<section title="Header Field Definitions" anchor="header.fields">
1928<t>
1929   This section defines the syntax and semantics of HTTP/1.1 header fields
1930   related to request and response semantics.
1931</t>
1932
1933<section title="Allow" anchor="header.allow">
1934  <iref primary="true" item="Allow header" x:for-anchor=""/>
1935  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1936  <x:anchor-alias value="Allow"/>
1937  <x:anchor-alias value="Allow-v"/>
1938<t>
1939   The "Allow" response-header field lists the set of methods advertised as
1940   supported by the target resource. The purpose of
1941   this field is strictly to inform the recipient of valid methods
1942   associated with the resource.
1943</t>
1944<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1945  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1946  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1947</artwork></figure>
1948<t>
1949      Example of use:
1950</t>
1951<figure><artwork type="example">
1952  Allow: GET, HEAD, PUT
1953</artwork></figure>
1954<t>
1955      The actual set of allowed methods is defined
1956      by the origin server at the time of each request.
1957</t>
1958<t>
1959      A proxy &MUST-NOT; modify the Allow header field even if it does not
1960      understand all the methods specified, since the user agent might
1961      have other means of communicating with the origin server.
1962</t>
1963</section>
1964
1965<section title="Expect" anchor="header.expect">
1966  <iref primary="true" item="Expect header" x:for-anchor=""/>
1967  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1968  <x:anchor-alias value="Expect"/>
1969  <x:anchor-alias value="Expect-v"/>
1970  <x:anchor-alias value="expectation"/>
1971  <x:anchor-alias value="expectation-extension"/>
1972  <x:anchor-alias value="expect-params"/>
1973<t>
1974   The "Expect" request-header field is used to indicate that particular
1975   server behaviors are required by the client.
1976</t>
1977<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1978  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1979  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1980 
1981  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1982  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1983                           *<x:ref>expect-params</x:ref> ]
1984  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1985</artwork></figure>
1986<t>
1987   A server that does not understand or is unable to comply with any of
1988   the expectation values in the Expect field of a request &MUST; respond
1989   with appropriate error status code. The server &MUST; respond with a 417
1990   (Expectation Failed) status code if any of the expectations cannot be met
1991   or, if there are other problems with the request, some other 4xx
1992   status code.
1993</t>
1994<t>
1995   This header field is defined with extensible syntax to allow for
1996   future extensions. If a server receives a request containing an
1997   Expect field that includes an expectation-extension that it does not
1998   support, it &MUST; respond with a 417 (Expectation Failed) status code.
1999</t>
2000<t>
2001   Comparison of expectation values is case-insensitive for unquoted
2002   tokens (including the 100-continue token), and is case-sensitive for
2003   quoted-string expectation-extensions.
2004</t>
2005<t>
2006   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2007   return a 417 (Expectation Failed) status code if it receives a request
2008   with an expectation that it cannot meet. However, the Expect
2009   request-header itself is end-to-end; it &MUST; be forwarded if the
2010   request is forwarded.
2011</t>
2012<t>
2013   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2014   Expect header.
2015</t>
2016<t>
2017   See &use100; for the use of the 100 (Continue) status code.
2018</t>
2019</section>
2020
2021<section title="From" anchor="header.from">
2022  <iref primary="true" item="From header" x:for-anchor=""/>
2023  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
2024  <x:anchor-alias value="From"/>
2025  <x:anchor-alias value="From-v"/>
2026  <x:anchor-alias value="mailbox"/>
2027<t>
2028   The "From" request-header field, if given, &SHOULD; contain an Internet
2029   e-mail address for the human user who controls the requesting user
2030   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2031   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2032</t>
2033<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2034  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2035  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2036 
2037  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2038</artwork></figure>
2039<t>
2040   An example is:
2041</t>
2042<figure><artwork type="example">
2043  From: webmaster@example.org
2044</artwork></figure>
2045<t>
2046   This header field &MAY; be used for logging purposes and as a means for
2047   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2048   be used as an insecure form of access protection. The interpretation
2049   of this field is that the request is being performed on behalf of the
2050   person given, who accepts responsibility for the method performed. In
2051   particular, robot agents &SHOULD; include this header so that the
2052   person responsible for running the robot can be contacted if problems
2053   occur on the receiving end.
2054</t>
2055<t>
2056   The Internet e-mail address in this field &MAY; be separate from the
2057   Internet host which issued the request. For example, when a request
2058   is passed through a proxy the original issuer's address &SHOULD; be
2059   used.
2060</t>
2061<t>
2062   The client &SHOULD-NOT;  send the From header field without the user's
2063   approval, as it might conflict with the user's privacy interests or
2064   their site's security policy. It is strongly recommended that the
2065   user be able to disable, enable, and modify the value of this field
2066   at any time prior to a request.
2067</t>
2068</section>
2069
2070<section title="Location" anchor="header.location">
2071  <iref primary="true" item="Location header" x:for-anchor=""/>
2072  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2073  <x:anchor-alias value="Location"/>
2074  <x:anchor-alias value="Location-v"/>
2075<t>
2076   The "Location" response-header field is used to identify a newly created
2077   resource, or to redirect the recipient to a different location for
2078   completion of the request.
2079</t>
2080<t>
2081   For 201 (Created) responses, the Location is the URI of the new resource
2082   which was created by the request. For 3xx responses, the location &SHOULD;
2083   indicate the server's preferred URI for automatic redirection to the
2084   resource.
2085</t>
2086<t>
2087   The field value consists of a single URI-reference. When it has the form
2088   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2089   the final value is computed by resolving it against the effective request
2090   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2091</t>
2092<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2093  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2094  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2095</artwork></figure>
2096<figure>
2097<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2098<artwork type="example">
2099  Location: http://www.example.org/pub/WWW/People.html#tim
2100</artwork></figure><figure><artwork type="example">  Location: /index.html
2101</artwork></figure>
2102<t>
2103   There are circumstances in which a fragment identifier in a Location URI
2104   would not be appropriate:
2105   <list style="symbols">
2106      <t>With a 201 Created response, because in this usage the Location header
2107      specifies the URI for the entire created resource.</t>
2108      <t>With 305 Use Proxy.</t>
2109   </list>
2110</t>
2111<x:note>
2112  <t>
2113    <x:h>Note:</x:h> This specification does not define precedence rules
2114    for the case where the original URI, as navigated to by the user
2115    agent, and the Location header field value both contain fragment
2116    identifiers.
2117  </t>
2118</x:note>
2119<x:note>
2120  <t>
2121    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2122    from Location in that the Content-Location identifies the most specific
2123    resource corresponding to the enclosed representation.
2124    It is therefore possible for a response to contain header fields for
2125    both Location and Content-Location.
2126  </t>
2127</x:note>
2128</section>
2129
2130<section title="Max-Forwards" anchor="header.max-forwards">
2131  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2132  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2133  <x:anchor-alias value="Max-Forwards"/>
2134  <x:anchor-alias value="Max-Forwards-v"/>
2135<t>
2136   The "Max-Forwards" request-header field provides a mechanism with the
2137   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2138   methods to limit the number of times that the request is forwarded by
2139   proxies or gateways. This can be useful when the client is attempting to
2140   trace a request which appears to be failing or looping in mid-chain.
2141</t>
2142<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2143  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2144  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2145</artwork></figure>
2146<t>
2147   The Max-Forwards value is a decimal integer indicating the remaining
2148   number of times this request message can be forwarded.
2149</t>
2150<t>
2151   Each proxy or gateway recipient of a TRACE or OPTIONS request
2152   containing a Max-Forwards header field &MUST; check and update its
2153   value prior to forwarding the request. If the received value is zero
2154   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2155   respond as the final recipient. If the received Max-Forwards value is
2156   greater than zero, then the forwarded message &MUST; contain an updated
2157   Max-Forwards field with a value decremented by one (1).
2158</t>
2159<t>
2160   The Max-Forwards header field &MAY; be ignored for all other methods
2161   defined by this specification and for any extension methods for which
2162   it is not explicitly referred to as part of that method definition.
2163</t>
2164</section>
2165
2166<section title="Referer" anchor="header.referer">
2167  <iref primary="true" item="Referer header" x:for-anchor=""/>
2168  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2169  <x:anchor-alias value="Referer"/>
2170  <x:anchor-alias value="Referer-v"/>
2171<t>
2172   The "Referer" [sic] request-header field allows the client to specify the
2173   URI of the resource from which the effective request URI was obtained (the
2174   "referrer", although the header field is misspelled.).
2175</t>
2176<t>
2177   The Referer header allows servers to generate lists of back-links to
2178   resources for interest, logging, optimized caching, etc. It also allows
2179   obsolete or mistyped links to be traced for maintenance. Some servers use
2180   Referer as a means of controlling where they allow links from (so-called
2181   "deep linking"), but it should be noted that legitimate requests are not
2182   required to contain a Referer header field.
2183</t>
2184<t>
2185   If the effective request URI was obtained from a source that does not have its own
2186   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2187   sent with the value "about:blank", or not be sent at all. Note that this
2188   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2189</t>
2190<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2191  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2192  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2193</artwork></figure>
2194<t>
2195   Example:
2196</t>
2197<figure><artwork type="example">
2198  Referer: http://www.example.org/hypertext/Overview.html
2199</artwork></figure>
2200<t>
2201   If the field value is a relative URI, it &SHOULD; be interpreted
2202   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2203   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2204</t>
2205</section>
2206
2207<section title="Retry-After" anchor="header.retry-after">
2208  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2209  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2210  <x:anchor-alias value="Retry-After"/>
2211  <x:anchor-alias value="Retry-After-v"/>
2212<t>
2213   The response-header "Retry-After" field can be used with a 503 (Service
2214   Unavailable) response to indicate how long the service is expected to
2215   be unavailable to the requesting client. This field &MAY; also be used
2216   with any 3xx (Redirection) response to indicate the minimum time the
2217   user-agent is asked wait before issuing the redirected request.
2218</t>
2219<t>
2220   The value of this field can be either an HTTP-date or an integer number
2221   of seconds (in decimal) after the time of the response.
2222</t>
2223<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2224  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2225  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2226</artwork></figure>
2227<t anchor="rule.delta-seconds">
2228  <x:anchor-alias value="delta-seconds"/>
2229   Time spans are non-negative decimal integers, representing time in
2230   seconds.
2231</t>
2232<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2233  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2234</artwork></figure>
2235<t>
2236   Two examples of its use are
2237</t>
2238<figure><artwork type="example">
2239  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2240  Retry-After: 120
2241</artwork></figure>
2242<t>
2243   In the latter example, the delay is 2 minutes.
2244</t>
2245</section>
2246
2247<section title="Server" anchor="header.server">
2248  <iref primary="true" item="Server header" x:for-anchor=""/>
2249  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2250  <x:anchor-alias value="Server"/>
2251  <x:anchor-alias value="Server-v"/>
2252<t>
2253   The "Server" response-header field contains information about the
2254   software used by the origin server to handle the request.
2255</t>
2256<t>
2257   The field can contain multiple product tokens (&product-tokens;) and
2258   comments (&header-fields;) identifying the server and any significant
2259   subproducts. The product tokens are listed in order of their significance
2260   for identifying the application.
2261</t>
2262<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2263  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2264  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2265                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2266</artwork></figure>
2267<t>
2268   Example:
2269</t>
2270<figure><artwork type="example">
2271  Server: CERN/3.0 libwww/2.17
2272</artwork></figure>
2273<t>
2274   If the response is being forwarded through a proxy, the proxy
2275   application &MUST-NOT; modify the Server response-header. Instead, it
2276   &MUST; include a Via field (as described in &header-via;).
2277</t>
2278<x:note>
2279  <t>
2280    <x:h>Note:</x:h> Revealing the specific software version of the server might
2281    allow the server machine to become more vulnerable to attacks
2282    against software that is known to contain security holes. Server
2283    implementors are encouraged to make this field a configurable
2284    option.
2285  </t>
2286</x:note>
2287</section>
2288
2289<section title="User-Agent" anchor="header.user-agent">
2290  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2291  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2292  <x:anchor-alias value="User-Agent"/>
2293  <x:anchor-alias value="User-Agent-v"/>
2294<t>
2295   The "User-Agent" request-header field contains information about the
2296   user agent originating the request. This is for statistical purposes,
2297   the tracing of protocol violations, and automated recognition of user
2298   agents for the sake of tailoring responses to avoid particular user
2299   agent limitations.
2300</t>
2301<t>
2302   User agents &SHOULD; include this field with requests. The field can contain
2303   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2304   identifying the agent and any subproducts which form a significant part of
2305   the user agent. By convention, the product tokens are listed in order of
2306   their significance for identifying the application.
2307</t>
2308<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2309  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2310  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2311                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2312</artwork></figure>
2313<t>
2314   Example:
2315</t>
2316<figure><artwork type="example">
2317  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2318</artwork></figure>
2319</section>
2320
2321</section>
2322
2323<section title="IANA Considerations" anchor="IANA.considerations">
2324
2325<section title="Method Registry" anchor="method.registration">
2326<t>
2327  The registration procedure for HTTP Methods is defined by
2328  <xref target="method.registry"/> of this document.
2329</t>
2330<t>
2331   The HTTP Method Registry should be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2332   and be populated with the registrations below:
2333</t>
2334<?BEGININC p2-semantics.iana-methods ?>
2335<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2336<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2337   <ttcol>Method</ttcol>
2338   <ttcol>Safe</ttcol>
2339   <ttcol>Reference</ttcol>
2340   <c>CONNECT</c>
2341   <c>no</c>
2342   <c>
2343      <xref target="CONNECT"/>
2344   </c>
2345   <c>DELETE</c>
2346   <c>no</c>
2347   <c>
2348      <xref target="DELETE"/>
2349   </c>
2350   <c>GET</c>
2351   <c>yes</c>
2352   <c>
2353      <xref target="GET"/>
2354   </c>
2355   <c>HEAD</c>
2356   <c>yes</c>
2357   <c>
2358      <xref target="HEAD"/>
2359   </c>
2360   <c>OPTIONS</c>
2361   <c>yes</c>
2362   <c>
2363      <xref target="OPTIONS"/>
2364   </c>
2365   <c>POST</c>
2366   <c>no</c>
2367   <c>
2368      <xref target="POST"/>
2369   </c>
2370   <c>PUT</c>
2371   <c>no</c>
2372   <c>
2373      <xref target="PUT"/>
2374   </c>
2375   <c>TRACE</c>
2376   <c>yes</c>
2377   <c>
2378      <xref target="TRACE"/>
2379   </c>
2380</texttable>
2381<!--(END)-->
2382<?ENDINC p2-semantics.iana-methods ?>
2383</section>
2384
2385<section title="Status Code Registry" anchor="status.code.registration">
2386<t>
2387   The registration procedure for HTTP Status Codes -- previously defined
2388   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2389   by <xref target="status.code.registry"/> of this document.
2390</t>
2391<t>
2392   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2393   should be updated with the registrations below:
2394</t>
2395<?BEGININC p2-semantics.iana-status-codes ?>
2396<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2397<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2398   <ttcol>Value</ttcol>
2399   <ttcol>Description</ttcol>
2400   <ttcol>Reference</ttcol>
2401   <c>100</c>
2402   <c>Continue</c>
2403   <c>
2404      <xref target="status.100"/>
2405   </c>
2406   <c>101</c>
2407   <c>Switching Protocols</c>
2408   <c>
2409      <xref target="status.101"/>
2410   </c>
2411   <c>200</c>
2412   <c>OK</c>
2413   <c>
2414      <xref target="status.200"/>
2415   </c>
2416   <c>201</c>
2417   <c>Created</c>
2418   <c>
2419      <xref target="status.201"/>
2420   </c>
2421   <c>202</c>
2422   <c>Accepted</c>
2423   <c>
2424      <xref target="status.202"/>
2425   </c>
2426   <c>203</c>
2427   <c>Non-Authoritative Information</c>
2428   <c>
2429      <xref target="status.203"/>
2430   </c>
2431   <c>204</c>
2432   <c>No Content</c>
2433   <c>
2434      <xref target="status.204"/>
2435   </c>
2436   <c>205</c>
2437   <c>Reset Content</c>
2438   <c>
2439      <xref target="status.205"/>
2440   </c>
2441   <c>300</c>
2442   <c>Multiple Choices</c>
2443   <c>
2444      <xref target="status.300"/>
2445   </c>
2446   <c>301</c>
2447   <c>Moved Permanently</c>
2448   <c>
2449      <xref target="status.301"/>
2450   </c>
2451   <c>302</c>
2452   <c>Found</c>
2453   <c>
2454      <xref target="status.302"/>
2455   </c>
2456   <c>303</c>
2457   <c>See Other</c>
2458   <c>
2459      <xref target="status.303"/>
2460   </c>
2461   <c>305</c>
2462   <c>Use Proxy</c>
2463   <c>
2464      <xref target="status.305"/>
2465   </c>
2466   <c>306</c>
2467   <c>(Unused)</c>
2468   <c>
2469      <xref target="status.306"/>
2470   </c>
2471   <c>307</c>
2472   <c>Temporary Redirect</c>
2473   <c>
2474      <xref target="status.307"/>
2475   </c>
2476   <c>400</c>
2477   <c>Bad Request</c>
2478   <c>
2479      <xref target="status.400"/>
2480   </c>
2481   <c>402</c>
2482   <c>Payment Required</c>
2483   <c>
2484      <xref target="status.402"/>
2485   </c>
2486   <c>403</c>
2487   <c>Forbidden</c>
2488   <c>
2489      <xref target="status.403"/>
2490   </c>
2491   <c>404</c>
2492   <c>Not Found</c>
2493   <c>
2494      <xref target="status.404"/>
2495   </c>
2496   <c>405</c>
2497   <c>Method Not Allowed</c>
2498   <c>
2499      <xref target="status.405"/>
2500   </c>
2501   <c>406</c>
2502   <c>Not Acceptable</c>
2503   <c>
2504      <xref target="status.406"/>
2505   </c>
2506   <c>407</c>
2507   <c>Proxy Authentication Required</c>
2508   <c>
2509      <xref target="status.407"/>
2510   </c>
2511   <c>408</c>
2512   <c>Request Timeout</c>
2513   <c>
2514      <xref target="status.408"/>
2515   </c>
2516   <c>409</c>
2517   <c>Conflict</c>
2518   <c>
2519      <xref target="status.409"/>
2520   </c>
2521   <c>410</c>
2522   <c>Gone</c>
2523   <c>
2524      <xref target="status.410"/>
2525   </c>
2526   <c>411</c>
2527   <c>Length Required</c>
2528   <c>
2529      <xref target="status.411"/>
2530   </c>
2531   <c>413</c>
2532   <c>Request Entity Too Large</c>
2533   <c>
2534      <xref target="status.413"/>
2535   </c>
2536   <c>414</c>
2537   <c>URI Too Long</c>
2538   <c>
2539      <xref target="status.414"/>
2540   </c>
2541   <c>415</c>
2542   <c>Unsupported Media Type</c>
2543   <c>
2544      <xref target="status.415"/>
2545   </c>
2546   <c>417</c>
2547   <c>Expectation Failed</c>
2548   <c>
2549      <xref target="status.417"/>
2550   </c>
2551   <c>500</c>
2552   <c>Internal Server Error</c>
2553   <c>
2554      <xref target="status.500"/>
2555   </c>
2556   <c>501</c>
2557   <c>Not Implemented</c>
2558   <c>
2559      <xref target="status.501"/>
2560   </c>
2561   <c>502</c>
2562   <c>Bad Gateway</c>
2563   <c>
2564      <xref target="status.502"/>
2565   </c>
2566   <c>503</c>
2567   <c>Service Unavailable</c>
2568   <c>
2569      <xref target="status.503"/>
2570   </c>
2571   <c>504</c>
2572   <c>Gateway Timeout</c>
2573   <c>
2574      <xref target="status.504"/>
2575   </c>
2576   <c>505</c>
2577   <c>HTTP Version Not Supported</c>
2578   <c>
2579      <xref target="status.505"/>
2580   </c>
2581</texttable>
2582<!--(END)-->
2583<?ENDINC p2-semantics.iana-status-codes ?>
2584</section>
2585<section title="Header Field Registration" anchor="header.field.registration">
2586<t>
2587   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2588   with the permanent registrations below (see <xref target="RFC3864"/>):
2589</t>
2590<?BEGININC p2-semantics.iana-headers ?>
2591<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2592<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2593   <ttcol>Header Field Name</ttcol>
2594   <ttcol>Protocol</ttcol>
2595   <ttcol>Status</ttcol>
2596   <ttcol>Reference</ttcol>
2597
2598   <c>Allow</c>
2599   <c>http</c>
2600   <c>standard</c>
2601   <c>
2602      <xref target="header.allow"/>
2603   </c>
2604   <c>Expect</c>
2605   <c>http</c>
2606   <c>standard</c>
2607   <c>
2608      <xref target="header.expect"/>
2609   </c>
2610   <c>From</c>
2611   <c>http</c>
2612   <c>standard</c>
2613   <c>
2614      <xref target="header.from"/>
2615   </c>
2616   <c>Location</c>
2617   <c>http</c>
2618   <c>standard</c>
2619   <c>
2620      <xref target="header.location"/>
2621   </c>
2622   <c>Max-Forwards</c>
2623   <c>http</c>
2624   <c>standard</c>
2625   <c>
2626      <xref target="header.max-forwards"/>
2627   </c>
2628   <c>Referer</c>
2629   <c>http</c>
2630   <c>standard</c>
2631   <c>
2632      <xref target="header.referer"/>
2633   </c>
2634   <c>Retry-After</c>
2635   <c>http</c>
2636   <c>standard</c>
2637   <c>
2638      <xref target="header.retry-after"/>
2639   </c>
2640   <c>Server</c>
2641   <c>http</c>
2642   <c>standard</c>
2643   <c>
2644      <xref target="header.server"/>
2645   </c>
2646   <c>User-Agent</c>
2647   <c>http</c>
2648   <c>standard</c>
2649   <c>
2650      <xref target="header.user-agent"/>
2651   </c>
2652</texttable>
2653<!--(END)-->
2654<?ENDINC p2-semantics.iana-headers ?>
2655<t>
2656   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2657</t>
2658</section>
2659</section>
2660
2661<section title="Security Considerations" anchor="security.considerations">
2662<t>
2663   This section is meant to inform application developers, information
2664   providers, and users of the security limitations in HTTP/1.1 as
2665   described by this document. The discussion does not include
2666   definitive solutions to the problems revealed, though it does make
2667   some suggestions for reducing security risks.
2668</t>
2669
2670<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2671<t>
2672   Like any generic data transfer protocol, HTTP cannot regulate the
2673   content of the data that is transferred, nor is there any a priori
2674   method of determining the sensitivity of any particular piece of
2675   information within the context of any given request. Therefore,
2676   applications &SHOULD; supply as much control over this information as
2677   possible to the provider of that information. Four header fields are
2678   worth special mention in this context: Server, Via, Referer and From.
2679</t>
2680<t>
2681   Revealing the specific software version of the server might allow the
2682   server machine to become more vulnerable to attacks against software
2683   that is known to contain security holes. Implementors &SHOULD; make the
2684   Server header field a configurable option.
2685</t>
2686<t>
2687   Proxies which serve as a portal through a network firewall &SHOULD;
2688   take special precautions regarding the transfer of header information
2689   that identifies the hosts behind the firewall. In particular, they
2690   &SHOULD; remove, or replace with sanitized versions, any Via fields
2691   generated behind the firewall.
2692</t>
2693<t>
2694   The Referer header allows reading patterns to be studied and reverse
2695   links drawn. Although it can be very useful, its power can be abused
2696   if user details are not separated from the information contained in
2697   the Referer. Even when the personal information has been removed, the
2698   Referer header might indicate a private document's URI whose
2699   publication would be inappropriate.
2700</t>
2701<t>
2702   The information sent in the From field might conflict with the user's
2703   privacy interests or their site's security policy, and hence it
2704   &SHOULD-NOT;  be transmitted without the user being able to disable,
2705   enable, and modify the contents of the field. The user &MUST; be able
2706   to set the contents of this field within a user preference or
2707   application defaults configuration.
2708</t>
2709<t>
2710   We suggest, though do not require, that a convenient toggle interface
2711   be provided for the user to enable or disable the sending of From and
2712   Referer information.
2713</t>
2714<t>
2715   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2716   fields can sometimes be used to determine that a specific client or
2717   server have a particular security hole which might be exploited.
2718   Unfortunately, this same information is often used for other valuable
2719   purposes for which HTTP currently has no better mechanism.
2720</t>
2721<t>
2722   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2723   that was sent in request headers within the body of their response.
2724   Clients &SHOULD; be careful with sensitive information, like Cookies,
2725   Authorization credentials and other headers that might be used to
2726   collect data from the client.
2727</t> 
2728</section>
2729
2730<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2731<t>
2732   Because the source of a link might be private information or might
2733   reveal an otherwise private information source, it is strongly
2734   recommended that the user be able to select whether or not the
2735   Referer field is sent. For example, a browser client could have a
2736   toggle switch for browsing openly/anonymously, which would
2737   respectively enable/disable the sending of Referer and From
2738   information.
2739</t>
2740<t>
2741   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2742   HTTP request if the referring page was transferred with a secure
2743   protocol.
2744</t>
2745<t>
2746   Authors of services should not use GET-based forms for the submission of
2747   sensitive data because that data will be encoded in the request-target. Many
2748   existing servers, proxies, and user agents log or display the request-target
2749   in places where it might be visible to third parties. Such services can
2750   use POST-based form submission instead.
2751</t>
2752</section>
2753
2754<section title="Location Headers and Spoofing" anchor="location.spoofing">
2755<t>
2756   If a single server supports multiple organizations that do not trust
2757   one another, then it &MUST; check the values of Location and Content-Location
2758   headers in responses that are generated under control of
2759   said organizations to make sure that they do not attempt to
2760   invalidate resources over which they have no authority.
2761</t>
2762</section>
2763
2764</section>
2765
2766<section title="Acknowledgments" anchor="ack">
2767</section>
2768</middle>
2769<back>
2770
2771<references title="Normative References">
2772
2773<reference anchor="Part1">
2774  <front>
2775    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2776    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2777      <organization abbrev="Day Software">Day Software</organization>
2778      <address><email>fielding@gbiv.com</email></address>
2779    </author>
2780    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2781      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2782      <address><email>jg@freedesktop.org</email></address>
2783    </author>
2784    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2785      <organization abbrev="HP">Hewlett-Packard Company</organization>
2786      <address><email>JeffMogul@acm.org</email></address>
2787    </author>
2788    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2789      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2790      <address><email>henrikn@microsoft.com</email></address>
2791    </author>
2792    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2793      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2794      <address><email>LMM@acm.org</email></address>
2795    </author>
2796    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2797      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2798      <address><email>paulle@microsoft.com</email></address>
2799    </author>
2800    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2801      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2802      <address><email>timbl@w3.org</email></address>
2803    </author>
2804    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2805      <organization abbrev="W3C">World Wide Web Consortium</organization>
2806      <address><email>ylafon@w3.org</email></address>
2807    </author>
2808    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2809      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2810      <address><email>julian.reschke@greenbytes.de</email></address>
2811    </author>
2812    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2813  </front>
2814  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2815  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2816</reference>
2817
2818<reference anchor="Part3">
2819  <front>
2820    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2821    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2822      <organization abbrev="Day Software">Day Software</organization>
2823      <address><email>fielding@gbiv.com</email></address>
2824    </author>
2825    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2826      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2827      <address><email>jg@freedesktop.org</email></address>
2828    </author>
2829    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2830      <organization abbrev="HP">Hewlett-Packard Company</organization>
2831      <address><email>JeffMogul@acm.org</email></address>
2832    </author>
2833    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2834      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2835      <address><email>henrikn@microsoft.com</email></address>
2836    </author>
2837    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2838      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2839      <address><email>LMM@acm.org</email></address>
2840    </author>
2841    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2842      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2843      <address><email>paulle@microsoft.com</email></address>
2844    </author>
2845    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2846      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2847      <address><email>timbl@w3.org</email></address>
2848    </author>
2849    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2850      <organization abbrev="W3C">World Wide Web Consortium</organization>
2851      <address><email>ylafon@w3.org</email></address>
2852    </author>
2853    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2854      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2855      <address><email>julian.reschke@greenbytes.de</email></address>
2856    </author>
2857    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2858  </front>
2859  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2860  <x:source href="p3-payload.xml" basename="p3-payload"/>
2861</reference>
2862
2863<reference anchor="Part4">
2864  <front>
2865    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2866    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2867      <organization abbrev="Day Software">Day Software</organization>
2868      <address><email>fielding@gbiv.com</email></address>
2869    </author>
2870    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2871      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2872      <address><email>jg@freedesktop.org</email></address>
2873    </author>
2874    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2875      <organization abbrev="HP">Hewlett-Packard Company</organization>
2876      <address><email>JeffMogul@acm.org</email></address>
2877    </author>
2878    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2879      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2880      <address><email>henrikn@microsoft.com</email></address>
2881    </author>
2882    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2883      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2884      <address><email>LMM@acm.org</email></address>
2885    </author>
2886    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2887      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2888      <address><email>paulle@microsoft.com</email></address>
2889    </author>
2890    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2891      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2892      <address><email>timbl@w3.org</email></address>
2893    </author>
2894    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2895      <organization abbrev="W3C">World Wide Web Consortium</organization>
2896      <address><email>ylafon@w3.org</email></address>
2897    </author>
2898    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2899      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2900      <address><email>julian.reschke@greenbytes.de</email></address>
2901    </author>
2902    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2903  </front>
2904  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2905  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2906</reference>
2907
2908<reference anchor="Part5">
2909  <front>
2910    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2911    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2912      <organization abbrev="Day Software">Day Software</organization>
2913      <address><email>fielding@gbiv.com</email></address>
2914    </author>
2915    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2916      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2917      <address><email>jg@freedesktop.org</email></address>
2918    </author>
2919    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2920      <organization abbrev="HP">Hewlett-Packard Company</organization>
2921      <address><email>JeffMogul@acm.org</email></address>
2922    </author>
2923    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2924      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2925      <address><email>henrikn@microsoft.com</email></address>
2926    </author>
2927    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2928      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2929      <address><email>LMM@acm.org</email></address>
2930    </author>
2931    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2932      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2933      <address><email>paulle@microsoft.com</email></address>
2934    </author>
2935    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2936      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2937      <address><email>timbl@w3.org</email></address>
2938    </author>
2939    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2940      <organization abbrev="W3C">World Wide Web Consortium</organization>
2941      <address><email>ylafon@w3.org</email></address>
2942    </author>
2943    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2944      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2945      <address><email>julian.reschke@greenbytes.de</email></address>
2946    </author>
2947    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2948  </front>
2949  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2950  <x:source href="p5-range.xml" basename="p5-range"/>
2951</reference>
2952
2953<reference anchor="Part6">
2954  <front>
2955    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2956    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2957      <organization abbrev="Day Software">Day Software</organization>
2958      <address><email>fielding@gbiv.com</email></address>
2959    </author>
2960    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2961      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2962      <address><email>jg@freedesktop.org</email></address>
2963    </author>
2964    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2965      <organization abbrev="HP">Hewlett-Packard Company</organization>
2966      <address><email>JeffMogul@acm.org</email></address>
2967    </author>
2968    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2969      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2970      <address><email>henrikn@microsoft.com</email></address>
2971    </author>
2972    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2973      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2974      <address><email>LMM@acm.org</email></address>
2975    </author>
2976    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2977      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2978      <address><email>paulle@microsoft.com</email></address>
2979    </author>
2980    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2981      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2982      <address><email>timbl@w3.org</email></address>
2983    </author>
2984    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2985      <organization abbrev="W3C">World Wide Web Consortium</organization>
2986      <address><email>ylafon@w3.org</email></address>
2987    </author>
2988    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2989      <address><email>mnot@mnot.net</email></address>
2990    </author>
2991    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2992      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2993      <address><email>julian.reschke@greenbytes.de</email></address>
2994    </author>
2995    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2996  </front>
2997  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2998  <x:source href="p6-cache.xml" basename="p6-cache"/>
2999</reference>
3000
3001<reference anchor="Part7">
3002  <front>
3003    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3004    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3005      <organization abbrev="Day Software">Day Software</organization>
3006      <address><email>fielding@gbiv.com</email></address>
3007    </author>
3008    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3009      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3010      <address><email>jg@freedesktop.org</email></address>
3011    </author>
3012    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3013      <organization abbrev="HP">Hewlett-Packard Company</organization>
3014      <address><email>JeffMogul@acm.org</email></address>
3015    </author>
3016    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3017      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3018      <address><email>henrikn@microsoft.com</email></address>
3019    </author>
3020    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3021      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3022      <address><email>LMM@acm.org</email></address>
3023    </author>
3024    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3025      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3026      <address><email>paulle@microsoft.com</email></address>
3027    </author>
3028    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3029      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3030      <address><email>timbl@w3.org</email></address>
3031    </author>
3032    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3033      <organization abbrev="W3C">World Wide Web Consortium</organization>
3034      <address><email>ylafon@w3.org</email></address>
3035    </author>
3036    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3037      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3038      <address><email>julian.reschke@greenbytes.de</email></address>
3039    </author>
3040    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3041  </front>
3042  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3043  <x:source href="p7-auth.xml" basename="p7-auth"/>
3044</reference>
3045
3046<reference anchor="RFC2119">
3047  <front>
3048    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3049    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3050      <organization>Harvard University</organization>
3051      <address><email>sob@harvard.edu</email></address>
3052    </author>
3053    <date month="March" year="1997"/>
3054  </front>
3055  <seriesInfo name="BCP" value="14"/>
3056  <seriesInfo name="RFC" value="2119"/>
3057</reference>
3058
3059<reference anchor="RFC3986">
3060 <front>
3061  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3062  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3063    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3064    <address>
3065       <email>timbl@w3.org</email>
3066       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3067    </address>
3068  </author>
3069  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3070    <organization abbrev="Day Software">Day Software</organization>
3071    <address>
3072      <email>fielding@gbiv.com</email>
3073      <uri>http://roy.gbiv.com/</uri>
3074    </address>
3075  </author>
3076  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3077    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3078    <address>
3079      <email>LMM@acm.org</email>
3080      <uri>http://larry.masinter.net/</uri>
3081    </address>
3082  </author>
3083  <date month='January' year='2005'></date>
3084 </front>
3085 <seriesInfo name="RFC" value="3986"/>
3086 <seriesInfo name="STD" value="66"/>
3087</reference>
3088
3089<reference anchor="RFC5234">
3090  <front>
3091    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3092    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3093      <organization>Brandenburg InternetWorking</organization>
3094      <address>
3095        <email>dcrocker@bbiw.net</email>
3096      </address> 
3097    </author>
3098    <author initials="P." surname="Overell" fullname="Paul Overell">
3099      <organization>THUS plc.</organization>
3100      <address>
3101        <email>paul.overell@thus.net</email>
3102      </address>
3103    </author>
3104    <date month="January" year="2008"/>
3105  </front>
3106  <seriesInfo name="STD" value="68"/>
3107  <seriesInfo name="RFC" value="5234"/>
3108</reference>
3109
3110</references>
3111
3112<references title="Informative References">
3113
3114<reference anchor="RFC1945">
3115  <front>
3116    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3117    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3118      <organization>MIT, Laboratory for Computer Science</organization>
3119      <address><email>timbl@w3.org</email></address>
3120    </author>
3121    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3122      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3123      <address><email>fielding@ics.uci.edu</email></address>
3124    </author>
3125    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3126      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3127      <address><email>frystyk@w3.org</email></address>
3128    </author>
3129    <date month="May" year="1996"/>
3130  </front>
3131  <seriesInfo name="RFC" value="1945"/>
3132</reference>
3133
3134<reference anchor="RFC2068">
3135  <front>
3136    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3137    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3138      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3139      <address><email>fielding@ics.uci.edu</email></address>
3140    </author>
3141    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3142      <organization>MIT Laboratory for Computer Science</organization>
3143      <address><email>jg@w3.org</email></address>
3144    </author>
3145    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3146      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3147      <address><email>mogul@wrl.dec.com</email></address>
3148    </author>
3149    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3150      <organization>MIT Laboratory for Computer Science</organization>
3151      <address><email>frystyk@w3.org</email></address>
3152    </author>
3153    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3154      <organization>MIT Laboratory for Computer Science</organization>
3155      <address><email>timbl@w3.org</email></address>
3156    </author>
3157    <date month="January" year="1997"/>
3158  </front>
3159  <seriesInfo name="RFC" value="2068"/>
3160</reference>
3161
3162<reference anchor="RFC2616">
3163  <front>
3164    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3165    <author initials="R." surname="Fielding" fullname="R. Fielding">
3166      <organization>University of California, Irvine</organization>
3167      <address><email>fielding@ics.uci.edu</email></address>
3168    </author>
3169    <author initials="J." surname="Gettys" fullname="J. Gettys">
3170      <organization>W3C</organization>
3171      <address><email>jg@w3.org</email></address>
3172    </author>
3173    <author initials="J." surname="Mogul" fullname="J. Mogul">
3174      <organization>Compaq Computer Corporation</organization>
3175      <address><email>mogul@wrl.dec.com</email></address>
3176    </author>
3177    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3178      <organization>MIT Laboratory for Computer Science</organization>
3179      <address><email>frystyk@w3.org</email></address>
3180    </author>
3181    <author initials="L." surname="Masinter" fullname="L. Masinter">
3182      <organization>Xerox Corporation</organization>
3183      <address><email>masinter@parc.xerox.com</email></address>
3184    </author>
3185    <author initials="P." surname="Leach" fullname="P. Leach">
3186      <organization>Microsoft Corporation</organization>
3187      <address><email>paulle@microsoft.com</email></address>
3188    </author>
3189    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3190      <organization>W3C</organization>
3191      <address><email>timbl@w3.org</email></address>
3192    </author>
3193    <date month="June" year="1999"/>
3194  </front>
3195  <seriesInfo name="RFC" value="2616"/>
3196</reference>
3197
3198<reference anchor='RFC2817'>
3199  <front>
3200    <title>Upgrading to TLS Within HTTP/1.1</title>
3201    <author initials='R.' surname='Khare' fullname='R. Khare'>
3202      <organization>4K Associates / UC Irvine</organization>
3203      <address><email>rohit@4K-associates.com</email></address>
3204    </author>
3205    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3206      <organization>Agranat Systems, Inc.</organization>
3207      <address><email>lawrence@agranat.com</email></address>
3208    </author>
3209    <date year='2000' month='May' />
3210  </front>
3211  <seriesInfo name='RFC' value='2817' />
3212</reference>
3213
3214<reference anchor='RFC3864'>
3215  <front>
3216    <title>Registration Procedures for Message Header Fields</title>
3217    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3218      <organization>Nine by Nine</organization>
3219      <address><email>GK-IETF@ninebynine.org</email></address>
3220    </author>
3221    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3222      <organization>BEA Systems</organization>
3223      <address><email>mnot@pobox.com</email></address>
3224    </author>
3225    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3226      <organization>HP Labs</organization>
3227      <address><email>JeffMogul@acm.org</email></address>
3228    </author>
3229    <date year='2004' month='September' />
3230  </front>
3231  <seriesInfo name='BCP' value='90' />
3232  <seriesInfo name='RFC' value='3864' />
3233</reference>
3234
3235<reference anchor='RFC5226'>
3236  <front>
3237    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3238    <author initials='T.' surname='Narten' fullname='T. Narten'>
3239      <organization>IBM</organization>
3240      <address><email>narten@us.ibm.com</email></address>
3241    </author>
3242    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3243      <organization>Google</organization>
3244      <address><email>Harald@Alvestrand.no</email></address>
3245    </author>
3246    <date year='2008' month='May' />
3247  </front>
3248  <seriesInfo name='BCP' value='26' />
3249  <seriesInfo name='RFC' value='5226' />
3250</reference>
3251
3252<reference anchor="RFC5322">
3253  <front>
3254    <title>Internet Message Format</title>
3255    <author initials="P." surname="Resnick" fullname="P. Resnick">
3256      <organization>Qualcomm Incorporated</organization>
3257    </author>
3258    <date year="2008" month="October"/>
3259  </front> 
3260  <seriesInfo name="RFC" value="5322"/>
3261</reference>
3262
3263</references>
3264
3265<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3266<t>
3267  This document takes over the Status Code Registry, previously defined
3268  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3269  (<xref target="status.code.registry"/>)
3270</t>
3271<t>
3272  Clarify definition of POST.
3273  (<xref target="POST"/>)
3274</t>
3275<t>
3276  Failed to consider that there are
3277  many other request methods that are safe to automatically redirect,
3278  and further that the user agent is able to make that determination
3279  based on the request method semantics.
3280  (Sections <xref format="counter" target="status.301"/>,
3281  <xref format="counter" target="status.302"/> and
3282  <xref format="counter" target="status.307"/>)
3283</t>
3284<t>
3285  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3286  It used to indicate that the target resource must be accessed through the
3287  proxy given by the Location field. The Location field gave the URI of the
3288  proxy. The recipient was expected to repeat this single request via the proxy.
3289  (<xref target="status.305"/>)
3290</t>
3291<t>
3292  Reclassify Allow header as response header, removing the option to
3293  specify it in a PUT request.
3294  Relax the server requirement on the contents of the Allow header and
3295  remove requirement on clients to always trust the header value.
3296  (<xref target="header.allow"/>)
3297</t>
3298<t>
3299  Correct syntax of Location header to allow URI references (including
3300  relative references and fragments), as referred symbol "absoluteURI" wasn't
3301  what was expected, and add some clarifications as to when use of fragments
3302  would not be appropriate.
3303  (<xref target="header.location"/>)
3304</t>
3305<t>
3306  Allow Referer value of "about:blank" as alternative to not specifying it.
3307  (<xref target="header.referer"/>)
3308</t>
3309<t>
3310  In the description of the Server header, the Via field
3311  was described as a SHOULD. The requirement was and is stated
3312  correctly in the description of the Via header in &header-via;.
3313  (<xref target="header.server"/>)
3314</t>
3315</section>
3316
3317<?BEGININC p2-semantics.abnf-appendix ?>
3318<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3319<figure>
3320<artwork type="abnf" name="p2-semantics.parsed-abnf">
3321<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3322<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3323<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3324<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3325<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3326<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3327<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3328<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3329<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3330
3331<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3332<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3333<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3334
3335<x:ref>From</x:ref> = "From:" OWS From-v
3336<x:ref>From-v</x:ref> = mailbox
3337
3338<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3339<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3340
3341<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3342If-Modified-Since =
3343 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3344<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3345<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3346If-Unmodified-Since =
3347 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3348
3349<x:ref>Location</x:ref> = "Location:" OWS Location-v
3350<x:ref>Location-v</x:ref> = URI-reference
3351
3352<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3353<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3354<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3355 / %x47.45.54 ; GET
3356 / %x48.45.41.44 ; HEAD
3357 / %x50.4F.53.54 ; POST
3358 / %x50.55.54 ; PUT
3359 / %x44.45.4C.45.54.45 ; DELETE
3360 / %x54.52.41.43.45 ; TRACE
3361 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3362 / extension-method
3363
3364<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3365
3366Proxy-Authenticate =
3367 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3368Proxy-Authorization =
3369 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3370
3371<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3372<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3373<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3374<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3375<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3376<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3377<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3378
3379<x:ref>Server</x:ref> = "Server:" OWS Server-v
3380<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3381<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3382 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3383 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3384 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3385 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3386 "505" / extension-code
3387
3388<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3389
3390<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3391<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3392<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3393
3394<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3395
3396WWW-Authenticate =
3397 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3398
3399<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3400
3401<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3402
3403<x:ref>delta-seconds</x:ref> = 1*DIGIT
3404
3405<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3406<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3407<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3408 *expect-params ]
3409<x:ref>extension-code</x:ref> = 3DIGIT
3410<x:ref>extension-method</x:ref> = token
3411
3412<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3413
3414<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3415
3416<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3417<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3418
3419<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3420
3421<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3422 Accept-Language / Authorization / Expect / From / Host / If-Match /
3423 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3424 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3425 User-Agent
3426<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3427 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3428
3429<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3430</artwork>
3431</figure>
3432<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3433; Reason-Phrase defined but not used
3434; Status-Code defined but not used
3435; request-header defined but not used
3436; response-header defined but not used
3437</artwork></figure></section>
3438<?ENDINC p2-semantics.abnf-appendix ?>
3439
3440<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3441
3442<section title="Since RFC2616">
3443<t>
3444  Extracted relevant partitions from <xref target="RFC2616"/>.
3445</t>
3446</section>
3447
3448<section title="Since draft-ietf-httpbis-p2-semantics-00">
3449<t>
3450  Closed issues:
3451  <list style="symbols"> 
3452    <t>
3453      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3454      "Via is a MUST"
3455      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3456    </t>
3457    <t>
3458      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3459      "Fragments allowed in Location"
3460      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3461    </t>
3462    <t>
3463      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3464      "Safe Methods vs Redirection"
3465      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3466    </t>
3467    <t>
3468      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3469      "Revise description of the POST method"
3470      (<eref target="http://purl.org/NET/http-errata#post"/>)
3471    </t>
3472    <t>
3473      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3474      "Normative and Informative references"
3475    </t>
3476    <t>
3477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3478      "RFC2606 Compliance"
3479    </t>
3480    <t>
3481      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3482      "Informative references"
3483    </t>
3484    <t>
3485      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3486      "Redundant cross-references"
3487    </t>
3488  </list>
3489</t>
3490<t>
3491  Other changes:
3492  <list style="symbols"> 
3493    <t>
3494      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3495    </t>
3496  </list>
3497</t>
3498</section>
3499
3500<section title="Since draft-ietf-httpbis-p2-semantics-01">
3501<t>
3502  Closed issues:
3503  <list style="symbols"> 
3504    <t>
3505      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3506      "PUT side effects"
3507    </t>
3508    <t>
3509      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3510      "Duplicate Host header requirements"
3511    </t>
3512  </list>
3513</t>
3514<t>
3515  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3516  <list style="symbols"> 
3517    <t>
3518      Move "Product Tokens" section (back) into Part 1, as "token" is used
3519      in the definition of the Upgrade header.
3520    </t>
3521    <t>
3522      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3523    </t>
3524    <t>
3525      Copy definition of delta-seconds from Part6 instead of referencing it.
3526    </t>
3527  </list>
3528</t>
3529</section>
3530
3531<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3532<t>
3533  Closed issues:
3534  <list style="symbols"> 
3535    <t>
3536      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3537      "Requiring Allow in 405 responses"
3538    </t>
3539    <t>
3540      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3541      "Status Code Registry"
3542    </t>
3543    <t>
3544      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3545      "Redirection vs. Location"
3546    </t>
3547    <t>
3548      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3549      "Cacheability of 303 response"
3550    </t>
3551    <t>
3552      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3553      "305 Use Proxy"
3554    </t>
3555    <t>
3556      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3557      "Classification for Allow header"
3558    </t>
3559    <t>
3560      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3561      "PUT - 'store under' vs 'store at'"
3562    </t>
3563  </list>
3564</t>
3565<t>
3566  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3567  <list style="symbols"> 
3568    <t>
3569      Reference RFC 3984, and update header registrations for headers defined
3570      in this document.
3571    </t>
3572  </list>
3573</t>
3574<t>
3575  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3576  <list style="symbols"> 
3577    <t>
3578      Replace string literals when the string really is case-sensitive (method).
3579    </t>
3580  </list>
3581</t>
3582</section>
3583
3584<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3585<t>
3586  Closed issues:
3587  <list style="symbols"> 
3588    <t>
3589      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3590      "OPTIONS request bodies"
3591    </t>
3592    <t>
3593      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3594      "Description of CONNECT should refer to RFC2817"
3595    </t>
3596    <t>
3597      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3598      "Location Content-Location reference request/response mixup"
3599    </t>
3600  </list>
3601</t>
3602<t>
3603  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3604  <list style="symbols"> 
3605    <t>
3606      Added initial proposal for registration process, plus initial
3607      content (non-HTTP/1.1 methods to be added by a separate specification).
3608    </t>
3609  </list>
3610</t>
3611</section>
3612
3613<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3614<t>
3615  Closed issues:
3616  <list style="symbols"> 
3617    <t>
3618      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3619      "Content-*"
3620    </t>
3621    <t>
3622      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3623      "RFC 2822 is updated by RFC 5322"
3624    </t>
3625  </list>
3626</t>
3627<t>
3628  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3629  <list style="symbols"> 
3630    <t>
3631      Use "/" instead of "|" for alternatives.
3632    </t>
3633    <t>
3634      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3635      whitespace ("OWS") and required whitespace ("RWS").
3636    </t>
3637    <t>
3638      Rewrite ABNFs to spell out whitespace rules, factor out
3639      header value format definitions.
3640    </t>
3641  </list>
3642</t>
3643</section>
3644
3645<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3646<t>
3647  Closed issues:
3648  <list style="symbols"> 
3649    <t>
3650      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3651      "Reason-Phrase BNF"
3652    </t>
3653  </list>
3654</t>
3655<t>
3656  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3657  <list style="symbols"> 
3658    <t>
3659      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3660    </t>
3661  </list>
3662</t>
3663</section>
3664
3665<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3666<t>
3667  Closed issues:
3668  <list style="symbols"> 
3669    <t>
3670      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3671      "Clarify when Referer is sent"
3672    </t>
3673    <t>
3674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3675      "status codes vs methods"
3676    </t>
3677    <t>
3678      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3679      "Do not require "updates" relation for specs that register status codes or method names"
3680    </t>
3681  </list>
3682</t>
3683</section>
3684
3685<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3686<t>
3687  Closed issues:
3688  <list style="symbols"> 
3689    <t>
3690      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3691      "Idempotency"
3692    </t>
3693    <t>
3694      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3695      "TRACE security considerations"
3696    </t>
3697    <t>
3698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3699      "Clarify rules for determining what entities a response carries"
3700    </t>
3701    <t>
3702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3703      "update note citing RFC 1945 and 2068"
3704    </t>
3705    <t>
3706      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3707      "update note about redirect limit"
3708    </t>
3709    <t>
3710      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3711      "Location header ABNF should use 'URI'"
3712    </t>
3713    <t>
3714      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3715      "fragments in Location vs status 303"
3716    </t>
3717    <t>
3718      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3719      "move IANA registrations for optional status codes"
3720    </t>
3721  </list>
3722</t>
3723<t>
3724  Partly resolved issues:
3725  <list style="symbols"> 
3726    <t>
3727      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3728      "Are OPTIONS and TRACE safe?"
3729    </t>
3730  </list>
3731</t>
3732</section>
3733
3734<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3735<t>
3736  Closed issues:
3737  <list style="symbols"> 
3738    <t>
3739      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3740      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3741      status codes when fixing this previously)
3742    </t>
3743  </list>
3744</t>
3745</section>
3746
3747<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3748<t>
3749  Closed issues:
3750  <list style="symbols"> 
3751    <t>
3752      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3753      "Fragment combination / precedence during redirects"
3754    </t>
3755  </list>
3756</t>
3757<t>
3758  Partly resolved issues:
3759  <list style="symbols"> 
3760    <t>
3761      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3762      "Location header payload handling"
3763    </t>
3764    <t>
3765      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3766      "Term for the requested resource's URI"
3767    </t>
3768  </list>
3769</t>
3770</section>
3771
3772<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3773<t>
3774  Closed issues:
3775  <list style="symbols"> 
3776    <t>
3777      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3778      "Clarify 'Requested Variant'"
3779    </t>
3780    <t>
3781      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3782      "Clarify entity / representation / variant terminology"
3783    </t>
3784    <t>
3785      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3786      "Methods and Caching"
3787    </t>
3788    <t>
3789      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3790      "OPTIONS vs Max-Forwards"
3791    </t>
3792    <t>
3793      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3794      "Status codes and caching"
3795    </t>
3796    <t>
3797      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3798      "consider removing the 'changes from 2068' sections"
3799    </t>
3800  </list>
3801</t>
3802</section>
3803
3804</section>
3805
3806</back>
3807</rfc>
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