Changeset 966 for draft-ietf-httpbis/latest/p4-conditional.html
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- 30/07/10 06:12:22 (12 years ago)
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draft-ietf-httpbis/latest/p4-conditional.html
r964 r966 627 627 <div id="rfc.figure.u.2"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">HTTP-date</a> = <HTTP-date, defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#date.time.formats.full.date" title="Date/Time Formats: Full Date">Section 6.1</a>> 628 628 </pre><h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a> <a id="entity.tags" href="#entity.tags">Entity-Tags</a></h1> 629 <p id="rfc.section.2.p.1">Entity-tags are used for comparing two or more representations from the same requested resource. HTTP/1.1 uses entity-tags630 in the ETag(<a href="#header.etag" id="rfc.xref.header.etag.1" title="ETag">Section 6.1</a>), If-Match (<a href="#header.if-match" id="rfc.xref.header.if-match.1" title="If-Match">Section 6.2</a>), If-None-Match (<a href="#header.if-none-match" id="rfc.xref.header.if-none-match.1" title="If-None-Match">Section 6.4</a>), and If-Range (<a href="p5-range.html#header.if-range" title="If-Range">Section 5.3</a> of <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>) header fields. The definition of how they are used and compared as cache validators is in <a href="#weak.and.strong.validators" title="Weak and Strong Validators">Section 4</a>. An entity-tag consists of an opaque quoted string, possibly prefixed by a weakness indicator.629 <p id="rfc.section.2.p.1">Entity-tags are used for comparing two or more representations of the same resource. HTTP/1.1 uses entity-tags in the ETag 630 (<a href="#header.etag" id="rfc.xref.header.etag.1" title="ETag">Section 6.1</a>), If-Match (<a href="#header.if-match" id="rfc.xref.header.if-match.1" title="If-Match">Section 6.2</a>), If-None-Match (<a href="#header.if-none-match" id="rfc.xref.header.if-none-match.1" title="If-None-Match">Section 6.4</a>), and If-Range (<a href="p5-range.html#header.if-range" title="If-Range">Section 5.3</a> of <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>) header fields. The definition of how they are used and compared as cache validators is in <a href="#weak.and.strong.validators" title="Weak and Strong Validators">Section 4</a>. An entity-tag consists of an opaque quoted string, possibly prefixed by a weakness indicator. 631 631 </p> 632 632 <div id="rfc.figure.u.3"></div><pre class="inline"><span id="rfc.iref.g.1"></span><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span> <a href="#entity.tags" class="smpl">entity-tag</a> = [ <a href="#entity.tags" class="smpl">weak</a> ] <a href="#entity.tags" class="smpl">opaque-tag</a> … … 642 642 </p> 643 643 <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a> <a id="example.entity.tag.vs.conneg" href="#example.entity.tag.vs.conneg">Example: Entity-tags varying on Content-Negotiated Resources</a></h2> 644 <p id="rfc.section.2.1.p.1">Consider a resource that is subject to content negotiation (<a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 4</a> of <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>), and where the representations returned upon a GET request vary based on the Accept-Encoding request header field (<a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 5.3</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>):644 <p id="rfc.section.2.1.p.1">Consider a resource that is subject to content negotiation (<a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>), and where the representations returned upon a GET request vary based on the Accept-Encoding request header field (<a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 6.3</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>): 645 645 </p> 646 646 <div id="rfc.figure.u.4"></div> … … 893 893 <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a> <a id="header.fields" href="#header.fields">Header Field Definitions</a></h1> 894 894 <p id="rfc.section.6.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to conditional requests.</p> 895 <p id="rfc.section.6.p.2">For entity-header fields, both sender and recipient refer to either the client or the server, depending on who sends and who896 receives the message.897 </p>898 895 <div id="rfc.iref.e.1"></div> 899 896 <div id="rfc.iref.h.1"></div> 900 897 <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> 901 <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 resource identified by the Effective Request URI. An entity-tag is intended for use as a resource-local898 <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 resource identified by the effective request URI. An entity-tag is intended for use as a resource-local 902 899 identifier for differentiating between representations of the same resource that vary over time or via content negotiation 903 900 (see <a href="#weak.and.strong.validators" title="Weak and Strong Validators">Section 4</a>). … … 1063 1060 <div id="rfc.iref.h.6"></div> 1064 1061 <h2 id="rfc.section.6.6"><a href="#rfc.section.6.6">6.6</a> <a id="header.last-modified" href="#header.last-modified">Last-Modified</a></h2> 1065 <p id="rfc.section.6.6.p.1">The "Last-Modified" entity-header field indicates the date and time at which the origin server believes the representation1066 was lastmodified.1062 <p id="rfc.section.6.6.p.1">The "Last-Modified" header field indicates the date and time at which the origin server believes the representation was last 1063 modified. 1067 1064 </p> 1068 1065 <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.14"></span><span id="rfc.iref.g.15"></span> <a href="#header.last-modified" class="smpl">Last-Modified</a> = "Last-Modified" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.last-modified" class="smpl">Last-Modified-v</a> … … 1084 1081 <p id="rfc.section.6.6.p.8">HTTP/1.1 servers <em class="bcp14">SHOULD</em> send Last-Modified whenever feasible. 1085 1082 </p> 1086 <p id="rfc.section.6.6.p.9">The Last-Modified entity-header field value is often used as a cache validator. In simple terms, a cache entry is considered1087 to bevalid if the representation has not been modified since the Last-Modified value.1083 <p id="rfc.section.6.6.p.9">The Last-Modified header field value is often used as a cache validator. In simple terms, a cache entry is considered to be 1084 valid if the representation has not been modified since the Last-Modified value. 1088 1085 </p> 1089 1086 <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a> <a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1> … … 1450 1447 </li> 1451 1448 <li class="indline1"><em>Part3</em> <a class="iref" href="#rfc.xref.Part3.1">2.1</a>, <a class="iref" href="#rfc.xref.Part3.2">2.1</a>, <a class="iref" href="#Part3"><b>10.1</b></a><ul class="ind"> 1452 <li class="indline1"><em>Section 4</em> <a class="iref" href="#rfc.xref.Part3.1">2.1</a></li>1453 <li class="indline1"><em>Section 5.3</em> <a class="iref" href="#rfc.xref.Part3.2">2.1</a></li>1449 <li class="indline1"><em>Section 5</em> <a class="iref" href="#rfc.xref.Part3.1">2.1</a></li> 1450 <li class="indline1"><em>Section 6.3</em> <a class="iref" href="#rfc.xref.Part3.2">2.1</a></li> 1454 1451 </ul> 1455 1452 </li>
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