Changeset 1876 for draft-ietf-httpbis/latest/p2-semantics.xml
- Timestamp:
- 10/09/12 08:28:31 (10 years ago)
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draft-ietf-httpbis/latest/p2-semantics.xml
r1875 r1876 106 106 <!ENTITY deflate-coding "<xref target='Part1' x:rel='#deflate.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 107 107 <!ENTITY gzip-coding "<xref target='Part1' x:rel='#gzip.coding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>"> 108 <!ENTITY response-representation "<xref target='identifying.response.associated.with.representation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">109 108 ]> 110 109 <?rfc toc="yes" ?> … … 290 289 <iref item="representation"/> 291 290 <t> 292 A "<x:dfn>representation</x:dfn>" is information in a format that can be readily 293 communicated from one party to another. A resource representation 294 is information that reflects the state of that resource, as observed 295 at some point in the past (e.g., in a response to GET) or to be 296 desired at some point in the future (e.g., in a PUT request). 297 </t> 298 <t> 299 Most, but not all, representations transferred via HTTP are intended 300 to be a representation of the target resource (the resource identified 301 by the effective request URI). The precise semantics of a representation 302 are determined by the type of message (request or response), the request 303 method, the response status code, and the representation metadata. For 304 example, the above semantic is true for the representation in any 305 <x:ref>200 (OK)</x:ref> response to GET and for the representation in any PUT request. 306 A 200 response to PUT, in contrast, contains either a representation 307 that describes the successful action or a representation of the target 308 resource, with the latter indicated by a <x:ref>Content-Location</x:ref> 309 header field with the same value as the effective request URI. Likewise, 310 response messages with an error status code usually contain a representation 311 that describes the error and what next steps are suggested for resolving it. 312 </t> 313 <t> 314 Request and Response messages &MAY; transfer a representation if not otherwise 315 restricted by the request method or response status code. A representation 316 consists of metadata (representation header fields) and data (representation 317 body). When a complete or partial representation is enclosed in an HTTP message, 318 it is referred to as the payload of the message. 291 If we consider that a resource could be anything, and that the uniform 292 interface provided by HTTP is similar to a window through which one 293 can observe and act upon such a thing only through the communication of 294 messages to some independent actor on the other side, then we need an 295 abstraction to represent ("take the place of") the current or desired state 296 of that thing in our communications. We call that abstraction a 297 "<x:dfn>representation</x:dfn>" <xref target="REST"/>. 298 </t> 299 <t> 300 For the purposes of HTTP, a <x:dfn>representation</x:dfn> is information 301 that reflects the current or desired state of a given resource, in a format 302 that can be readily communicated via the protocol, consisting of a set of 303 metadata (representation header fields) and a potentially unbounded stream 304 of data (representation body). 305 </t> 306 <t> 307 HTTP messages can transfer a full or partial representation in the payload 308 (<xref target="payload"/>) if not otherwise restricted by the request 309 method or response status code. In a request, the purpose of such a 310 representation is defined by the method semantics. In a response, the 311 purpose is defined by both the request method and the response status code. 312 </t> 313 <t> 314 For example, a representation in the payload of a PUT request 315 (<xref target="PUT"/>) represents the desired state of the target resource 316 if the request is successfully applied, whereas a representation in the 317 payload of a POST request (<xref target="POST"/>) represents an anonymous 318 resource for providing data to be processed, such as a specific encoding 319 format for the information that a user entered within an HTML form. 320 </t> 321 <t> 322 Likewise, the payload of a <x:ref>200 (OK)</x:ref> response to GET 323 (<xref target="GET"/>) contains a representation of the target resource, 324 as observed at the time of the message origination date 325 (<xref target="header.date"/>), whereas the same response to POST might 326 contain either a representation of the processing result or a current 327 representation of the target resource after applying the processing. 328 Response messages with an error status code usually contain a 329 representation that describes the error and what next steps are suggested 330 for resolving it. 319 331 </t> 320 332 <t> … … 325 337 </t> 326 338 327 <section title=" Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">339 <section title="Associating a Representation with its Resource" anchor="associating.representation.with.resource"> 328 340 <t> 329 341 It is sometimes necessary to determine an identifier for the resource … … 4232 4244 not allowed), and can define how to determine the resource which they 4233 4245 carry a representation for (see <xref 4234 target=" identifying.response.associated.with.representation"/>; by default,4246 target="associating.representation.with.resource"/>; by default, 4235 4247 it is anonymous). 4236 4248 </t>
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