The Hypertext Transfer Protocol (HTTP) Status Code 209 (Contents of Related)World Wide Web Consortium32 Vassar St.CambridgeMA02140USAeric@w3.orghttp://www.w3.org/People/Eric/ericP-foaf#ericPHTTPredirectstatus code
This document specifies the additional HyperText Transfer Protocol (HTTP)
Status Code 209 (Contents of Related).
Distribution of this document is unlimited. Although this is not a work
item of the HTTPbis Working Group, comments should be sent to the
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Test cases related to redirection in general and the status code 209 in particular can be found at as a template.
The HTTP 2xx status codes indicate that the client's request was successfully received, understood, and accepted.
The 209 status code response signals that Location field identifies a resource related to the requested resource and that the response contents are a representation of that related resource.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in .
The 209 (Contents of Related) status code indicates that the server is redirecting the user agent to a different resource, as indicated by a URI in the Location header field, that is intended to provide an indirect response to the original request.
The contents of the response are a representation of the resource identified in the Location header field.
The 209 response bypasses the extra round trip required for use cases conventionally solved with a 303 (See Other) response followed by the client performing a second GET on the target of that redirect.
For example, 209 streamlines these uses of 303 response codes:
An HTTP client performs a GET on a resource which is not an information resource.
The server responsd with a 303 and the client performs a second GET to retrieve an information resource related to the previous resource.
(This idiom is frequently used to provide informative content about resources which specifically distinct from any page describing them.)
An HTTP server responds to a POST request by creating a new resource and using a 303 response code to redirect the client to that new resource.
(This use case is described in .)
The resource requested in a GET is prohibitively large to serve and the server instead responds with a redirect to beginning of a series of resoures paginating the initial resource.
The paginating resources are interlinked with the 'prev' and 'next' link headers described in .
All header fields other than Location are equivalent to those required in a response to a GET for the resource that is the target of the Location header.
Caching semantics are for the response are the same as for a 200 response to a GET on the target resource, though it is not necessary to include the Location header field as it is identical to the effective Request URI.
Additionally, the 209 response to the initial request MAY be cached but it MUST include the Location header field in cached responses.
Thus, a 209 response can be seen as providing two cache entries, a 200 response for the resource expressed in the Location header field and a 209 response for the initial resource.
Client request:Server response:
http://example.com/p1 may be cached with a response code of 200 and http://example.com/hardToGet may be cached with a response code of 209.
Section 4 of specified that all 2xx status codes indicate a successful request.
However, some conventional clients may not be specifically programmed to accept content accompanying a 2xx response other than 200.
Therefore, initial use of status code 209 will be restricted to cases where the server has sufficient confidence in the clients understanding the new code.
A client MAY indicate that it expects a 209 status code with a header like "Prefer: follow-link rel=first".
All security considerations that apply to either 303 or 200 response codes apply also to the 209 status code (see Section 12 of ).
The registration below shall be added to the HTTP Status Code Registry
(defined in Section 4.2 of
and located at ):
ValueDescriptionReference209Contents of Related of this specification
The definition for the new status code 209 re-uses text from
the HTTP/1.1 definitions of 2xx status codes.
The structure and much of the text of this draft was taken from Key words for use in RFCs to Indicate Requirement LevelsHarvard Universitysob@harvard.eduUniform Resource Identifier (URI): Generic SyntaxWorld Wide Web Consortiumtimbl@w3.orghttp://www.w3.org/People/Berners-Lee/Day Softwarefielding@gbiv.comhttp://roy.gbiv.com/Adobe Systems IncorporatedLMM@acm.orghttp://larry.masinter.net/HTTP/1.1, part 1: URIs, Connections, and Message ParsingAdobe Systems Incorporatedfielding@gbiv.comWorld Wide Web Consortiumylafon@w3.orggreenbytes GmbHjulian.reschke@greenbytes.deHTTP/1.1, part 2: Message SemanticsAdobe Systems Incorporatedfielding@gbiv.comWorld Wide Web Consortiumylafon@w3.orggreenbytes GmbHjulian.reschke@greenbytes.deHTTP/1.1, part 6: CachingAdobe Systems Incorporatedfielding@gbiv.comWorld Wide Web Consortiumylafon@w3.orgRackspacemnot@mnot.netgreenbytes GmbHjulian.reschke@greenbytes.deTURTLE 4.01 Specification
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