Changeset 163 for draft-ietf-httpbis/latest/p4-conditional.html
- Timestamp:
- 12/01/08 05:09:10 (14 years ago)
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draft-ietf-httpbis/latest/p4-conditional.html
r160 r163 521 521 </ul> 522 522 <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a> <a id="introduction" href="#introduction">Introduction</a></h1> 523 <p id="rfc.section.1.p.1">This document defines aspects of HTTP related to conditional request messages based on time stamps and entity-tags. Right 524 now it only includes the extracted relevant sections of <a href="#RFC2616">RFC 2616</a> <cite title="Hypertext Transfer Protocol -- HTTP/1.1" id="rfc.xref.RFC2616.1">[RFC2616]</cite> with only minor changes. This introduction will be revised in the next draft. 523 <p id="rfc.section.1.p.1">This document defines HTTP/1.1 response metadata for indicating potential changes to payload content, including modification 524 time stamps and opaque entity-tags, and the HTTP conditional request mechanisms that allow preconditions to be placed on a 525 request method. Conditional GET requests allow for efficient cache updates. Other conditional request methods are used to 526 protect against overwriting or misunderstanding the state of a resource that has been changed unbeknownst to the requesting 527 client. 528 </p> 529 <p id="rfc.section.1.p.2">This document is currently disorganized in order to minimize the changes between drafts and enable reviewers to see the smaller 530 errata changes. The next draft will reorganize the sections to better reflect the content. In particular, the sections on 531 resource metadata will be discussed first and then followed by each conditional request-header, concluding with a definition 532 of precedence and the expectation of ordering strong validator checks before weak validator checks. It is likely that more 533 content from <a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a> will migrate to this part, where appropriate. The current mess reflects how widely dispersed these topics and associated requirements 534 had become in <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>. 525 535 </p> 526 536 <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a> <a id="intro.requirements" href="#intro.requirements">Requirements</a></h2> … … 756 766 header <em class="bcp14">MUST</em> be ignored. 757 767 </p> 758 <p id="rfc.section.6.2.p.7">The meaning of "If-Match: *" is that the method <em class="bcp14">SHOULD</em> be performed if the representation selected by the origin server (or by a cache, possibly using the Vary mechanism, see <a href="p6-cache.html#header.vary" title="Vary">Section 15.5</a> of <a href="#Part6" id="rfc.xref.Part6. 1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) exists, and <em class="bcp14">MUST NOT</em> be performed if the representation does not exist.768 <p id="rfc.section.6.2.p.7">The meaning of "If-Match: *" is that the method <em class="bcp14">SHOULD</em> be performed if the representation selected by the origin server (or by a cache, possibly using the Vary mechanism, see <a href="p6-cache.html#header.vary" title="Vary">Section 15.5</a> of <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) exists, and <em class="bcp14">MUST NOT</em> be performed if the representation does not exist. 759 769 </p> 760 770 <p id="rfc.section.6.2.p.8">A request intended to update a resource (e.g., a PUT) <em class="bcp14">MAY</em> include an If-Match header field to signal that the request method <em class="bcp14">MUST NOT</em> be applied if the entity corresponding to the If-Match value (a single entity tag) is no longer a representation of that resource. … … 837 847 If-None-Match header <em class="bcp14">MUST</em> be ignored. (See <a href="#rules.for.when.to.use.entity.tags.and.last-modified.dates" title="Rules for When to Use Entity Tags and Last-Modified Dates">Section 5</a> for a discussion of server behavior when both If-Modified-Since and If-None-Match appear in the same request.) 838 848 </p> 839 <p id="rfc.section.6.4.p.8">The meaning of "If-None-Match: *" is that the method <em class="bcp14">MUST NOT</em> be performed if the representation selected by the origin server (or by a cache, possibly using the Vary mechanism, see <a href="p6-cache.html#header.vary" title="Vary">Section 15.5</a> of <a href="#Part6" id="rfc.xref.Part6. 2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) exists, and <em class="bcp14">SHOULD</em> be performed if the representation does not exist. This feature is intended to be useful in preventing races between PUT operations.849 <p id="rfc.section.6.4.p.8">The meaning of "If-None-Match: *" is that the method <em class="bcp14">MUST NOT</em> be performed if the representation selected by the origin server (or by a cache, possibly using the Vary mechanism, see <a href="p6-cache.html#header.vary" title="Vary">Section 15.5</a> of <a href="#Part6" id="rfc.xref.Part6.3"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) exists, and <em class="bcp14">SHOULD</em> be performed if the representation does not exist. This feature is intended to be useful in preventing races between PUT operations. 840 850 </p> 841 851 <p id="rfc.section.6.4.p.9">Examples:</p> … … 1064 1074 </ul> 1065 1075 </li> 1066 <li class="indline1"><em>Part6</em> <a class="iref" href="#rfc.xref.Part6.1"> 6.2</a>, <a class="iref" href="#rfc.xref.Part6.2">6.4</a>, <a class="iref" href="#Part6"><b>10.1</b></a><ul class="ind">1067 <li class="indline1"><em>Section 15.5</em> <a class="iref" href="#rfc.xref.Part6. 1">6.2</a>, <a class="iref" href="#rfc.xref.Part6.2">6.4</a></li>1076 <li class="indline1"><em>Part6</em> <a class="iref" href="#rfc.xref.Part6.1">1</a>, <a class="iref" href="#rfc.xref.Part6.2">6.2</a>, <a class="iref" href="#rfc.xref.Part6.3">6.4</a>, <a class="iref" href="#Part6"><b>10.1</b></a><ul class="ind"> 1077 <li class="indline1"><em>Section 15.5</em> <a class="iref" href="#rfc.xref.Part6.2">6.2</a>, <a class="iref" href="#rfc.xref.Part6.3">6.4</a></li> 1068 1078 </ul> 1069 1079 </li>
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