Changeset 1284 for draft-ietf-httpbis

Timestamp:

20/05/11 02:28:25 (10 years ago)

Author:

mnot@…

Message:

Rewrite Pragma section; addresses #292

Location:

draft-ietf-httpbis/latest

Files:

• p6-cache.html (modified) (11 diffs)
• p6-cache.xml (modified) (3 diffs)

draft-ietf-httpbis/latest/p6-cache.html

@@ -362 +362 @@
   } 
   @bottom-center {
-       content: "Expires November 5, 2011"; 
+       content: "Expires November 21, 2011"; 
   } 
   @bottom-right {
@@ -408 +408 @@
       <meta name="dct.creator" content="Reschke, J. F.">
       <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-p6-cache-latest">
-      <meta name="dct.issued" scheme="ISO8601" content="2011-05-04">
+      <meta name="dct.issued" scheme="ISO8601" content="2011-05-20">
       <meta name="dct.replaces" content="urn:ietf:rfc:2616">
       <meta name="dct.abstract" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. This document is Part 6 of the seven-part specification that defines the protocol referred to as &#34;HTTP/1.1&#34; and, taken together, obsoletes RFC 2616. Part 6 defines requirements on HTTP caches and the associated header fields that control cache behavior or indicate cacheable response messages.">
@@ -434 +434 @@
             </tr>
             <tr>
-               <td class="left">Expires: November 5, 2011</td>
+               <td class="left">Expires: November 21, 2011</td>
                <td class="right">J. Mogul</td>
             </tr>
@@ -495 +495 @@
             <tr>
                <td class="left"></td>
-               <td class="right">May 4, 2011</td>
+               <td class="right">May 20, 2011</td>
             </tr>
          </tbody>
@@ -523 +523 @@
          in progress”.
       </p>
-      <p>This Internet-Draft will expire on November 5, 2011.</p>
+      <p>This Internet-Draft will expire on November 21, 2011.</p>
       <h1><a id="rfc.copyrightnotice" href="#rfc.copyrightnotice">Copyright Notice</a></h1>
       <p>Copyright © 2011 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
@@ -1305 +1305 @@
       <div id="rfc.iref.h.5"></div>
       <h2 id="rfc.section.3.4"><a href="#rfc.section.3.4">3.4</a>&nbsp;<a id="header.pragma" href="#header.pragma">Pragma</a></h2>
-      <p id="rfc.section.3.4.p.1">The "Pragma" header field is used to include implementation-specific directives that might apply to any recipient along the
-         request/response chain. All pragma directives specify optional behavior from the viewpoint of the protocol; however, some
-         systems <em class="bcp14">MAY</em> require that behavior be consistent with the directives.
+      <p id="rfc.section.3.4.p.1">The "Pragma" header field allows backwards compatibility with HTTP/1.0 caches, so that clients can specify a "no-cache" request
+         that they will understand (as Cache-Control was not defined until HTTP/1.1). When the Cache-Control header is also present
+         and understood in a request, Pragma is ignored.
+      </p>
+      <p id="rfc.section.3.4.p.2">In HTTP/1.0, Pragma was defined as an extensible field for implementation-specified directives for recipients. This specification
+         deprecates such extensions to improve interoperability.
       </p>
       <div id="rfc.figure.u.15"></div><pre class="inline"><span id="rfc.iref.g.8"></span><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span>  <a href="#header.pragma" class="smpl">Pragma</a>           = 1#<a href="#header.pragma" class="smpl">pragma-directive</a>
   <a href="#header.pragma" class="smpl">pragma-directive</a> = "no-cache" / <a href="#header.pragma" class="smpl">extension-pragma</a>
   <a href="#header.pragma" class="smpl">extension-pragma</a> = <a href="#core.rules" class="smpl">token</a> [ "=" ( <a href="#core.rules" class="smpl">token</a> / <a href="#core.rules" class="smpl">quoted-string</a> ) ]
-</pre><p id="rfc.section.3.4.p.3">When the no-cache directive is present in a request message, a cache <em class="bcp14">SHOULD</em> forward the request toward the origin server even if it has a stored copy of what is being requested. This pragma directive
-         has the same semantics as the no-cache request directive (see <a href="#cache-request-directive" title="Request Cache-Control Directives">Section&nbsp;3.2.1</a>) and is defined here for backward compatibility with HTTP/1.0. A client <em class="bcp14">SHOULD</em> include both header fields when a no-cache request is sent to a server not known to be HTTP/1.1 compliant. A cache <em class="bcp14">SHOULD</em> treat "Pragma: no-cache" as if the client had sent "Cache-Control: no-cache".
-      </p>
-      <div class="note" id="rfc.section.3.4.p.4"> 
-         <p> <b>Note:</b> Because the meaning of "Pragma: no-cache" as a header field is not actually specified, it does not provide a reliable replacement
-            for "Cache-Control: no-cache" in a response.
+</pre><p id="rfc.section.3.4.p.4">When the Cache-Control header is not present in a request, the no-cache request pragma-directive <em class="bcp14">MUST</em> have the same effect on caches as if "Cache-Control: no-cache" were present (see <a href="#cache-request-directive" title="Request Cache-Control Directives">Section&nbsp;3.2.1</a>).
+      </p>
+      <p id="rfc.section.3.4.p.5">When sending a no-cache request, a client <em class="bcp14">SHOULD</em> include both pragma and cache-control directives unless Cache-Control: no-cache is purposefully omitted to target other Cache-Control
+         response directives at HTTP/1.1 caches. For example:
+      </p>
+      <div id="rfc.figure.u.16"></div> <pre class="text">GET / HTTP/1.1
+Host: www.example.com
+Cache-Control: max-age=30
+Pragma: no-cache
+</pre> <p id="rfc.section.3.4.p.7">will constrain HTTP/1.1 caches to serve a response no older than 30 seconds, while precluding implementations that do not
+         understand Cache-Control from serving a cached response.
+      </p>
+      <div class="note" id="rfc.section.3.4.p.8"> 
+         <p>Note: Because the meaning of "Pragma: no-cache" in responses is not specified, it does not provide a reliable replacement
+            for "Cache-Control: no-cache" in them.
          </p> 
       </div>
-      <p id="rfc.section.3.4.p.5">This mechanism is deprecated; no new Pragma directives will be defined in HTTP.</p>
       <div id="rfc.iref.v.2"></div>
       <div id="rfc.iref.h.6"></div>
@@ -1331 +1342 @@
          the representation.
       </p>
-      <div id="rfc.figure.u.16"></div><pre class="inline"><span id="rfc.iref.g.11"></span>  <a href="#header.vary" class="smpl">Vary</a> = "*" / 1#<a href="#abnf.dependencies" class="smpl">field-name</a>
+      <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.11"></span>  <a href="#header.vary" class="smpl">Vary</a> = "*" / 1#<a href="#abnf.dependencies" class="smpl">field-name</a>
 </pre><p id="rfc.section.3.5.p.5">The set of header fields named by the Vary field value is known as the selecting header fields.</p>
       <p id="rfc.section.3.5.p.6">A server <em class="bcp14">SHOULD</em> include a Vary header field with any cacheable response that is subject to server-driven negotiation. Doing so allows a cache
@@ -1358 +1369 @@
          be applied to response messages.
       </p>
-      <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.12"></span><span id="rfc.iref.g.13"></span><span id="rfc.iref.g.14"></span><span id="rfc.iref.g.15"></span><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span>  <a href="#header.warning" class="smpl">Warning</a>       = 1#<a href="#header.warning" class="smpl">warning-value</a>
+      <div id="rfc.figure.u.18"></div><pre class="inline"><span id="rfc.iref.g.12"></span><span id="rfc.iref.g.13"></span><span id="rfc.iref.g.14"></span><span id="rfc.iref.g.15"></span><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span>  <a href="#header.warning" class="smpl">Warning</a>       = 1#<a href="#header.warning" class="smpl">warning-value</a>
   
   <a href="#header.warning" class="smpl">warning-value</a> = <a href="#header.warning" class="smpl">warn-code</a> <a href="#notation" class="smpl">SP</a> <a href="#header.warning" class="smpl">warn-agent</a> <a href="#notation" class="smpl">SP</a> <a href="#header.warning" class="smpl">warn-text</a>
@@ -1709 +1720 @@
       </p>
       <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a id="collected.abnf" href="#collected.abnf">Collected ABNF</a></h1>
-      <div id="rfc.figure.u.18"></div> <pre class="inline"><a href="#header.age" class="smpl">Age</a> = delta-seconds
+      <div id="rfc.figure.u.19"></div> <pre class="inline"><a href="#header.age" class="smpl">Age</a> = delta-seconds
 
 <a href="#header.cache-control" class="smpl">Cache-Control</a> = *( "," OWS ) cache-directive *( OWS "," [ OWS
@@ -1764 +1775 @@
 <a href="#header.warning" class="smpl">warning-value</a> = warn-code SP warn-agent SP warn-text [ SP warn-date
  ]
-</pre> <div id="rfc.figure.u.19"></div>
+</pre> <div id="rfc.figure.u.20"></div>
       <p>ABNF diagnostics:</p><pre class="inline">; Age defined but not used
 ; Cache-Control defined but not used
@@ -1949 +1960 @@
       </ul>
       <h2 id="rfc.section.C.16"><a href="#rfc.section.C.16">C.16</a>&nbsp;<a id="changes.since.14" href="#changes.since.14">Since draft-ietf-httpbis-p6-cache-14</a></h2>
-      <p id="rfc.section.C.16.p.1">None yet.</p>
+      <p id="rfc.section.C.16.p.1">Closed issues: </p>
+      <ul>
+         <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/292">http://tools.ietf.org/wg/httpbis/trac/ticket/292</a>&gt;: "Pragma"
+         </li>
+      </ul>
       <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
       <p class="noprint"><a href="#rfc.index.A">A</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.E">E</a> <a href="#rfc.index.F">F</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.M">M</a> <a href="#rfc.index.N">N</a> <a href="#rfc.index.O">O</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a> <a href="#rfc.index.S">S</a> <a href="#rfc.index.V">V</a> <a href="#rfc.index.W">W</a> 

draft-ietf-httpbis/latest/p6-cache.xml

@@ -1502 +1502 @@
    <x:anchor-alias value="pragma-directive"/>
 <t>
-   The "Pragma" header field is used to include
-   implementation-specific directives that might apply to any recipient along
-   the request/response chain. All pragma directives specify optional behavior
-   from the viewpoint of the protocol; however, some systems &MAY; require
-   that behavior be consistent with the directives.
+         The "Pragma" header field allows backwards compatibility with HTTP/1.0
+   caches, so that clients can specify a "no-cache" request that they will
+   understand (as Cache-Control was not defined until HTTP/1.1). When the
+   Cache-Control header is also present and understood in a request, Pragma is
+   ignored.
+</t>
+<t>
+         In HTTP/1.0, Pragma was defined as an extensible field for
+   implementation-specified directives for recipients. This specification
+   deprecates such extensions to improve interoperability.
 </t>
 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Pragma"/><iref primary="true" item="Grammar" subitem="pragma-directive"/><iref primary="true" item="Grammar" subitem="extension-pragma"/>
@@ -1514 +1519 @@
 </artwork></figure>
 <t>
-   When the no-cache directive is present in a request message, a cache
-   &SHOULD; forward the request toward the origin server even if it has a
-   stored copy of what is being requested. This pragma directive has the same
-   semantics as the no-cache request directive (see <xref
-   target="cache-request-directive" />) and is defined here for backward
-   compatibility with HTTP/1.0. A client &SHOULD; include both header fields
-   when a no-cache request is sent to a server not known to be HTTP/1.1
-   compliant. A cache &SHOULD; treat "Pragma: no-cache" as if the
-   client had sent "Cache-Control: no-cache".
+         When the Cache-Control header is not present in a request, the no-cache
+   request pragma-directive &MUST; have the same effect on caches as if
+   "Cache-Control: no-cache" were present (see <xref
+   target="cache-request-directive" />).
+</t>
+<t>
+   When sending a no-cache request, a client &SHOULD; include both pragma and
+   cache-control directives unless Cache-Control: no-cache is purposefully
+   omitted to target other Cache-Control response directives at HTTP/1.1
+   caches. For example:
+</t>
+<figure>
+<artwork type="code">
+GET / HTTP/1.1
+Host: www.example.com
+Cache-Control: max-age=30
+Pragma: no-cache
+</artwork>
+</figure>
+<t>
+   will constrain HTTP/1.1 caches to serve a response no older than 30
+   seconds, while precluding implementations that do not understand
+   Cache-Control from serving a cached response.
 </t>
 <x:note>
    <t>
-      <x:h>Note:</x:h> Because the meaning of "Pragma: no-cache" as a
-      header field is not actually specified, it does not provide a
-      reliable replacement for "Cache-Control: no-cache" in a response.
-   </t>
+      Note: Because the meaning of "Pragma: no-cache" in responses is not
+      specified, it does not provide a reliable replacement for
+      "Cache-Control: no-cache" in them.
+         </t>
 </x:note>
-<t>
-   This mechanism is deprecated; no new Pragma directives will be defined in
-   HTTP.
-</t>
 </section>
 
@@ -2684 +2699 @@
 <section title="Since draft-ietf-httpbis-p6-cache-14" anchor="changes.since.14">
 <t>
-  None yet.
+  Closed issues:
+        <list style="symbols">
+                <t>
+                        <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/292"/>:
+                        "Pragma"
+                </t>
+        </list>
 </t>
 </section>