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Changeset 1164 for draft-ietf-httpbis/latest/p4-conditional.html
- Timestamp:
- 11/03/11 06:45:43 (10 years ago)
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draft-ietf-httpbis/latest/p4-conditional.html (modified) (8 diffs)
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draft-ietf-httpbis/latest/p4-conditional.html
r1162 r1164 605 605 <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 606 606 errata changes. A future draft will reorganize the sections to better reflect the content. In particular, the sections on 607 resource metadata will be discussed first and then followed by each conditional request -header field, concluding with a definition607 resource metadata will be discussed first and then followed by each conditional request header field, concluding with a definition 608 608 of precedence and the expectation of ordering strong validator checks before weak validator checks. It is likely that more 609 609 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 … … 708 708 <div id="rfc.iref.s.2"></div> 709 709 <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a> <a id="status.412" href="#status.412">412 Precondition Failed</a></h2> 710 <p id="rfc.section.3.2.p.1">The precondition given in one or more of the request-header fields evaluated to false when it was tested on the server. This711 response code allows the client to place preconditions on the current resource metadata (header field data) and thus prevent712 the requestedmethod from being applied to a resource other than the one intended.710 <p id="rfc.section.3.2.p.1">The precondition given in one or more of the header fields evaluated to false when it was tested on the server. This response 711 code allows the client to place preconditions on the current resource metadata (header field data) and thus prevent the requested 712 method from being applied to a resource other than the one intended. 713 713 </p> 714 714 <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a> <a id="weak.and.strong.validators" href="#weak.and.strong.validators">Weak and Strong Validators</a></h1> … … 904 904 <div id="rfc.iref.h.1"></div> 905 905 <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a> <a id="header.etag" href="#header.etag">ETag</a></h2> 906 <p id="rfc.section.6.1.p.1">The "ETag" response-header field provides the current value of the entity-tag (see <a href="#entity.tags" title="Entity-Tags">Section 2</a>) for one representation of the target resource. An entity-tag is intended for use as a resource-local identifier for differentiating906 <p id="rfc.section.6.1.p.1">The "ETag" header field provides the current value of the entity-tag (see <a href="#entity.tags" title="Entity-Tags">Section 2</a>) for one representation of the target resource. An entity-tag is intended for use as a resource-local identifier for differentiating 907 907 between representations of the same resource that vary over time or via content negotiation (see <a href="#weak.and.strong.validators" title="Weak and Strong Validators">Section 4</a>). 908 908 </p> … … 925 925 <div id="rfc.iref.h.2"></div> 926 926 <h2 id="rfc.section.6.2"><a href="#rfc.section.6.2">6.2</a> <a id="header.if-match" href="#header.if-match">If-Match</a></h2> 927 <p id="rfc.section.6.2.p.1">The "If-Match" request-header field is used to make a request method conditional. A client that has one or more representations928 previously obtained from the resource can verify that one of those representations is current by including a list of their929 associatedentity-tags in the If-Match header field.927 <p id="rfc.section.6.2.p.1">The "If-Match" header field is used to make a request method conditional. A client that has one or more representations previously 928 obtained from the resource can verify that one of those representations is current by including a list of their associated 929 entity-tags in the If-Match header field. 930 930 </p> 931 931 <p id="rfc.section.6.2.p.2">This allows efficient updates of cached information with a minimum amount of transaction overhead. It is also used when updating … … 960 960 <div id="rfc.iref.h.3"></div> 961 961 <h2 id="rfc.section.6.3"><a href="#rfc.section.6.3">6.3</a> <a id="header.if-modified-since" href="#header.if-modified-since">If-Modified-Since</a></h2> 962 <p id="rfc.section.6.3.p.1">The "If-Modified-Since" request-header field is used to make a request method conditional by date: if the representation that963 would have been transferred in a 200 response to a GET request has not been modified since the time specified in this field,964 thendo not perform the method; instead, respond as detailed below.962 <p id="rfc.section.6.3.p.1">The "If-Modified-Since" header field is used to make a request method conditional by date: if the representation that would 963 have been transferred in a 200 response to a GET request has not been modified since the time specified in this field, then 964 do not perform the method; instead, respond as detailed below. 965 965 </p> 966 966 <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.8"></span><span id="rfc.iref.g.9"></span> <a href="#header.if-modified-since" class="smpl">If-Modified-Since</a> = "If-Modified-Since" ":" <a href="#core.rules" class="smpl">OWS</a> … … 986 986 <p id="rfc.section.6.3.p.6">The purpose of this feature is to allow efficient updates of cached information with a minimum amount of transaction overhead. </p> 987 987 <ul class="empty"> 988 <li> <b>Note:</b> The Range request-header field modifies the meaning of If-Modified-Since; see <a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.4"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a> for full details.988 <li> <b>Note:</b> The Range header field modifies the meaning of If-Modified-Since; see <a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.4"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a> for full details. 989 989 </li> 990 990 <li> <b>Note:</b> If-Modified-Since times are interpreted by the server, whose clock might not be synchronized with the client. … … 1010 1010 <div id="rfc.iref.h.4"></div> 1011 1011 <h2 id="rfc.section.6.4"><a href="#rfc.section.6.4">6.4</a> <a id="header.if-none-match" href="#header.if-none-match">If-None-Match</a></h2> 1012 <p id="rfc.section.6.4.p.1">The "If-None-Match" request-header field is used to make a request method conditional. A client that has one or more representations1012 <p id="rfc.section.6.4.p.1">The "If-None-Match" header field is used to make a request method conditional. A client that has one or more representations 1013 1013 previously obtained from the resource can verify that none of those representations is current by including a list of their 1014 1014 associated entity-tags in the If-None-Match header field. … … 1046 1046 <div id="rfc.iref.h.5"></div> 1047 1047 <h2 id="rfc.section.6.5"><a href="#rfc.section.6.5">6.5</a> <a id="header.if-unmodified-since" href="#header.if-unmodified-since">If-Unmodified-Since</a></h2> 1048 <p id="rfc.section.6.5.p.1">The "If-Unmodified-Since" request-header field is used to make a request method conditional. If the representation that would1049 have been transferred in a 200 response to a GET request on the same resource has not been modified since the time specified1050 inthis field, the server <em class="bcp14">SHOULD</em> perform the requested operation as if the If-Unmodified-Since header field were not present.1048 <p id="rfc.section.6.5.p.1">The "If-Unmodified-Since" header field is used to make a request method conditional. If the representation that would have 1049 been transferred in a 200 response to a GET request on the same resource has not been modified since the time specified in 1050 this field, the server <em class="bcp14">SHOULD</em> perform the requested operation as if the If-Unmodified-Since header field were not present. 1051 1051 </p> 1052 1052 <p id="rfc.section.6.5.p.2">If the representation has been modified since the specified time, the server <em class="bcp14">MUST NOT</em> perform the requested operation, and <em class="bcp14">MUST</em> return a 412 (Precondition Failed).
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