< draft-dusseault-http-patch-15.txt   draft-dusseault-http-patch-16.txt >
Network Working Group L. Dusseault Network Working Group L. Dusseault
Internet-Draft Linden Lab Internet-Draft Linden Lab
Intended status: Standards Track J. Snell Intended status: Standards Track J. Snell
Expires: April 18, 2010 October 15, 2009 Expires: May 29, 2010 November 25, 2009
PATCH Method for HTTP PATCH Method for HTTP
draft-dusseault-http-patch-15 draft-dusseault-http-patch-16
Abstract
Several applications extending the Hypertext Transfer Protocol (HTTP)
require a feature to do partial resource modification. The existing
HTTP PUT method only allows a complete replacement of a document.
This proposal adds a new HTTP method, PATCH, to modify an existing
HTTP resource.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 1, line 32 skipping to change at page 1, line 40
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 18, 2010. This Internet-Draft will expire on May 29, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents
publication of this document (http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Abstract include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
Several applications extending the Hypertext Transfer Protocol (HTTP) described in the BSD License.
require a feature to do partial resource modification. The existing
HTTP PUT method only allows a complete replacement of a document.
This proposal adds a new HTTP method, PATCH, to modify an existing
HTTP resource.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The PATCH Method . . . . . . . . . . . . . . . . . . . . . . . 3 2. The PATCH Method . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. A simple PATCH example . . . . . . . . . . . . . . . . . . 5 2.1. A simple PATCH example . . . . . . . . . . . . . . . . . . 5
2.2. Error handling . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Error handling . . . . . . . . . . . . . . . . . . . . . . 5
3. Advertising Support in OPTIONS . . . . . . . . . . . . . . . . 6 3. Advertising Support in OPTIONS . . . . . . . . . . . . . . . . 7
3.1. The Accept-Patch Header . . . . . . . . . . . . . . . . . 7 3.1. The Accept-Patch Header . . . . . . . . . . . . . . . . . 7
3.2. Example OPTIONS Request and Response . . . . . . . . . . . 7 3.2. Example OPTIONS Request and Response . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4.1. The 'Accept-Patch' Response Header . . . . . . . . . . . . 7 4.1. The 'Accept-Patch' Response Header . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . . 8 6.1. Normative References . . . . . . . . . . . . . . . . . . . 9
6.2. Informative References . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . . 9 Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . . 10
B.1. Changes from -00 . . . . . . . . . . . . . . . . . . . . . 9 B.1. Changes from -00 . . . . . . . . . . . . . . . . . . . . . 10
B.2. Changes from -01 . . . . . . . . . . . . . . . . . . . . . 9 B.2. Changes from -01 . . . . . . . . . . . . . . . . . . . . . 10
B.3. Changes from -02 . . . . . . . . . . . . . . . . . . . . . 9 B.3. Changes from -02 . . . . . . . . . . . . . . . . . . . . . 10
B.4. Changes from -03 . . . . . . . . . . . . . . . . . . . . . 10 B.4. Changes from -03 . . . . . . . . . . . . . . . . . . . . . 11
B.5. Changes from -04 . . . . . . . . . . . . . . . . . . . . . 10 B.5. Changes from -04 . . . . . . . . . . . . . . . . . . . . . 11
B.6. Changes from -05 . . . . . . . . . . . . . . . . . . . . . 10 B.6. Changes from -05 . . . . . . . . . . . . . . . . . . . . . 11
B.7. Changes from -06 . . . . . . . . . . . . . . . . . . . . . 10 B.7. Changes from -06 . . . . . . . . . . . . . . . . . . . . . 11
B.8. Changes from -07 . . . . . . . . . . . . . . . . . . . . . 11 B.8. Changes from -07 . . . . . . . . . . . . . . . . . . . . . 11
B.9. Changes from -08 . . . . . . . . . . . . . . . . . . . . . 11 B.9. Changes from -08 . . . . . . . . . . . . . . . . . . . . . 12
B.10. Changes from -09 . . . . . . . . . . . . . . . . . . . . . 12 B.10. Changes from -09 . . . . . . . . . . . . . . . . . . . . . 12
B.11. Changes from -10 . . . . . . . . . . . . . . . . . . . . . 12 B.11. Changes from -10 . . . . . . . . . . . . . . . . . . . . . 12
B.12. Changes from -11 . . . . . . . . . . . . . . . . . . . . . 12 B.12. Changes from -11 . . . . . . . . . . . . . . . . . . . . . 13
B.13. Changes from -12 . . . . . . . . . . . . . . . . . . . . . 12 B.13. Changes from -12 . . . . . . . . . . . . . . . . . . . . . 13
B.14. Changes from -13 . . . . . . . . . . . . . . . . . . . . . 12 B.14. Changes from -13 . . . . . . . . . . . . . . . . . . . . . 13
B.15. Changes from -14 . . . . . . . . . . . . . . . . . . . . . 13 B.15. Changes from -14 . . . . . . . . . . . . . . . . . . . . . 13
Appendix C. Notes to RFC Editor . . . . . . . . . . . . . . . . . 13 B.16. Changes from -15 . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Appendix C. Notes to RFC Editor . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
This specification defines the new HTTP/1.1 [RFC2616] method PATCH This specification defines the new HTTP/1.1 [RFC2616] method PATCH
that is used to apply partial modifications to a resource. that is used to apply partial modifications to a resource.
A new method is necessary to improve interoperability and prevent A new method is necessary to improve interoperability and prevent
errors. The PUT method is already defined to overwrite a resource errors. The PUT method is already defined to overwrite a resource
with a complete new body, and can not be reused to do partial with a complete new body, and can not be reused to do partial
changes. Otherwise, proxies and caches and even clients and servers changes. Otherwise, proxies and caches and even clients and servers
may get confused as to the result of the operation. PATCH was may get confused as to the result of the operation. POST is already
mentioned in earlier HTTP specifications, but not completely defined. used but without broad interoperability (for one, there is no
standard way to discover patch format support). PATCH was mentioned
in earlier HTTP specifications, but not completely defined.
In this document, the key words "MUST", "MUST NOT", "REQUIRED", In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in [RFC2119]. and "OPTIONAL" are to be interpreted as described in [RFC2119].
Furthermore, this document uses the ABNF syntax defined in Section Furthermore, this document uses the ABNF syntax defined in Section
2.1 of [RFC2616]. 2.1 of [RFC2616].
2. The PATCH Method 2. The PATCH Method
The PATCH method requests that a set of changes described in the The PATCH method requests that a set of changes described in the
request entity be applied to the resource identified by the Request- request entity be applied to the resource identified by the Request-
URI. The set of changes is represented in a format called a "patch URI. The set of changes is represented in a format called a "patch
document" identified by a media type. If the Request-URI does not document" identified by a media type. If the Request-URI does not
point to an existing resource, the server MAY create a new resource, point to an existing resource, the server MAY create a new resource,
depending on the patch document type (whether it can logically modify depending on the patch document type (whether it can logically modify
a null resource) and permissions etc. a null resource) and permissions etc.
PATCH is neither safe or idempotent as defined by [RFC2616], Section
9.1.
The difference between the PUT and PATCH requests is reflected in the The difference between the PUT and PATCH requests is reflected in the
way the server processes the enclosed entity to modify the resource way the server processes the enclosed entity to modify the resource
identified by the Request-URI. In a PUT request, the enclosed entity identified by the Request-URI. In a PUT request, the enclosed entity
is considered to be a modified version of the resource stored on the is considered to be a modified version of the resource stored on the
origin server and the client is requesting that the stored version be origin server and the client is requesting that the stored version be
replaced. With PATCH, however, the enclosed entity contains a set of replaced. With PATCH, however, the enclosed entity contains a set of
instructions describing how a resource currently residing on the instructions describing how a resource currently residing on the
origin server should be modified to produce a new version. The PATCH origin server should be modified to produce a new version. The PATCH
method affects the resource identified by the Request-URI, and also method affects the resource identified by the Request-URI, and also
MAY have side effects on other resources; i.e., new resources may be MAY have side effects on other resources; i.e., new resources may be
created, or existing ones modified, by the application of a PATCH. created, or existing ones modified, by the application of a PATCH.
PATCH is neither safe or idempotent as defined by [RFC2616], Section
9.1.
A PATCH request can be issued in such a way as to be idempotent,
which also helps prevent bad outcomes from collisions between two
PATCH requests on the same resource in a similar timeframe.
Collisions from multiple PATCH requests may be more dangerous than
PUT collisions, because some patch formats need to operate from a
known base point or else corrupt the resource. Clients using this
kind of patch application SHOULD acquire a strong ETag [RFC2616] for
the resource to be modified, and use that ETag in the If-Match header
on the PATCH request to verify that the resource is still unchanged.
If a strong ETag is not available for a given resource, the client
can use If-Unmodified-Since as a less-reliable safeguard.
There are also cases where patch formats do not need to operate from
a known base-point (e.g. appending text lines to log files, or non-
colliding rows to database tables), in which case the same care in
client requests is not needed.
The server MUST apply the entire set of changes atomically and never The server MUST apply the entire set of changes atomically and never
provide (e.g. in response to a GET during this operation) a provide (e.g. in response to a GET during this operation) a
partially-modified representation. If the entire patch document partially-modified representation. If the entire patch document
cannot be successfully applied then the server MUST fail the entire cannot be successfully applied then the server MUST NOT apply any of
request, applying none of the changes. The determination of what the changes. The determination of what constitutes a successful
constitutes a successful PATCH can vary depending on the patch PATCH can vary depending on the patch document and the type of
document and the type of resource being modified. See Error Handling resource(s) being modified. For example, the common 'diff' utility
in Section 2.2 for details on status codes and possible error can generate a patch document that applies to multiple files in a
conditions. directory hierarchy. The atomicity requirement holds for all
directly affected files. See Error Handling in Section 2.2 for
details on status codes and possible error conditions.
If the request passes through a cache and the Request-URI identifies If the request passes through a cache and the Request-URI identifies
one or more currently cached entities, those entries SHOULD be one or more currently cached entities, those entries SHOULD be
treated as stale. A response to this method is only cacheable if it treated as stale. A response to this method is only cacheable if it
contains explicit freshness information (such as an Expires header or contains explicit freshness information (such as an Expires header or
"Cache-Control: max-age" directive) as well as the Content-Location "Cache-Control: max-age" directive) as well as the Content-Location
header matching the request-URI, indicating that the PATCH response header matching the request-URI, indicating that the PATCH response
body is a resource representation. A cached PATCH response can only body is a resource representation. A cached PATCH response can only
be used to respond to subsequent GET and HEAD requests; it MUST NOT be used to respond to subsequent GET and HEAD requests; it MUST NOT
be used to respond to other methods (in particular, PATCH). be used to respond to other methods (in particular, PATCH).
Collisions from multiple PATCH requests are more dangerous than PUT
collisions, because a patch document that is not operating from a
known base point may corrupt the resource. Clients wishing to apply
a patch document to a known entity can first acquire the strong ETag
[RFC2616] of the resource to be modified, and use that Etag in the
If-Match header on the PATCH request to verify that the resource is
still unchanged. If a strong ETag is not available for a given
resource, the client can use If-Unmodified-Since as a less-reliable
safeguard.
Note that entity-headers contained in the request apply only to the Note that entity-headers contained in the request apply only to the
contained patch document and MUST NOT be applied to the resource contained patch document and MUST NOT be applied to the resource
being modified. Thus, a Content-Language header could be present on being modified. Thus, a Content-Language header could be present on
the request but it would only mean (for whatever that's worth) that the request but it would only mean (for whatever that's worth) that
the patch document had a language. Servers SHOULD NOT store such the patch document had a language. Servers SHOULD NOT store such
headers except as trace information, and SHOULD NOT use such header headers except as trace information, and SHOULD NOT use such header
values the same way they might be used on PUT requests. Therefore, values the same way they might be used on PUT requests. Therefore,
this document does not specify a way to modify a document's Content- this document does not specify a way to modify a document's Content-
Type or Content-Language value through headers, though a mechanism Type or Content-Language value through headers, though a mechanism
could well be designed to achieve this goal through a patch document. could well be designed to achieve this goal through a patch document.
skipping to change at page 5, line 26 skipping to change at page 5, line 37
Host: www.example.com Host: www.example.com
Content-Type: application/example Content-Type: application/example
If-Match: "e0023aa4e" If-Match: "e0023aa4e"
Content-Length: 100 Content-Length: 100
[description of changes] [description of changes]
This example illustrates use of a hypothetical patch document on an This example illustrates use of a hypothetical patch document on an
existing resource. The 204 response code is used because the existing resource. The 204 response code is used because the
response does not have a body (a response with the 200 code would response does not have a body (a response with the 200 code would
have a body) but other success codes MAY be used if appropriate. have a body) but other success codes can be used if appropriate.
Successful PATCH response to existing text file Successful PATCH response to existing text file
HTTP/1.1 204 No Content HTTP/1.1 204 No Content
Content-Location: /file.txt
ETag: "e0023aa4f" ETag: "e0023aa4f"
2.2. Error handling 2.2. Error handling
There are several known conditions under which a PATCH request can There are several known conditions under which a PATCH request can
fail. fail.
Malformed patch document: Can be specified using a 400 (Bad Request) Malformed patch document: When the server determines that the patch
when the server finds that the patch document provided by the document provided by the client is not properly formatted, it
client was not properly formatted. The definition of badly SHOULD return a 400 (Bad Request) response. The definition of
formatted depends on the patch document chosen, but generally if badly formatted depends on the patch document chosen.
the server finds it cannot handle the patch due to the
serialization of the patch document, this response ought to be
appropriate.
Unsupported patch document: Can be specified using a 415 Unsupported patch document: Can be specified using a 415
(Unsupported Media Type) when the client sends a patch document (Unsupported Media Type) when the client sends a patch document
format that the server does not support for the resource format that the server does not support for the resource
identified by the Request-URI. Such a response SHOULD include an identified by the Request-URI. Such a response SHOULD include an
Accept-Patch response header as described in Section 3.1 to notify Accept-Patch response header as described in Section 3.1 to notify
the client what patch document formats are supported. the client what patch document media types are supported.
Unprocessable request: Can be specified with a 422 (Unprocessable Unprocessable request: Can be specified with a 422 (Unprocessable
Entity) ([RFC4918], Section 11.2) when the server understands the Entity) ([RFC4918], Section 11.2) when the server understands the
patch document and the syntax of the patch document appears valid, patch document and the syntax of the patch document appears valid,
but the server is incapable of processing the request. This might but the server is incapable of processing the request. This might
include attempts to modify a resource in a way that would cause include attempts to modify a resource in a way that would cause
the resource to become invalid: for instance, a modification to a the resource to become invalid: for instance, a modification to a
well-formed XML document that would cause it to no longer be well- well-formed XML document that would cause it to no longer be well-
formed. There may also be more specific errors like "Conflicting formed. There may also be more specific errors like "Conflicting
State" that could be signaled with this status code, but the more State" that could be signaled with this status code, but the more
specific error would generally be more helpful. specific error would generally be more helpful.
Resource Not Found: Can be specified with a 404 (Not Found) status Resource Not Found: Can be specified with a 404 (Not Found) status
code, when the client attempted to apply a patch document to a code, when the client attempted to apply a patch document to a
non-existent resource, but the patch document chosen cannot be non-existent resource, but the patch document chosen cannot be
applied to a non-existent resource. applied to a non-existent resource.
Conflicting State: Can be specified with a 409 (Conflict) when the Conflicting State: Can be specified with a 409 (Conflict) when the
request cannot be applied given the state of the resource. For request cannot be applied given the state of the resource. For
example, if the client attempted to apply a structural example, if the client attempted to apply a structural
modification and the structures assumed to exist did not exist modification and the structures assumed to exist did not exist
(with XML, a patch might specify changing element 'foo' to element (with XML, a patch might specify changing element 'foo' to element
'bar' but element 'foo' might not exist). 'bar' but element 'foo' might not exist).
Conflicting modification: Specified with a 412 (Precondition Failed) Conflicting modification: When a client uses either the If-Match or
when a client uses either the If-Match or If-Unmodified-Since If-Unmodified-Since header to define a precondition, and that
request headers and attempts to apply a patch document to a precondition failed, then the 412 (Precondition Failed) error is
resource whose state has changed since the patch was created. If most helpful to the client. However, that response makes no sense
the server detects a possible conflicting modification and neither if there was no precondition on the request. In cases when the
the If-Match or If-Unmodified-Since request headers are used, the server detects a possible conflicting modification and no
server can return a 409 (Conflict) response. precondition was defined in the request, the server can return a
Concurrent modification: When a server receives multiple concurrent 409 (Conflict) response.
requests to modify a resource, those requests SHOULD be queued and Concurrent modification: Some applications of PATCH might require
processed in the order in which they are received. If a server is the server to process requests in the order in which they are
incapable of queuing concurrent requests, all subsequent requests received. If a server is operating under those restrictions, and
SHOULD be rejected with a 409 (Conflict) until the first it receives concurrent requests to modify the same resource, but
modification request is complete. is unable to queue those requests, the server can usefully
indicate this error by using a 409 (Conflict) response.
Note that the 409 Conflict response gives reasonably consistent
information to clients. Depending on the application and the nature
of the patch format, the client might be able to reissue the request
as is (e.g. an instruction to append a line to a log file), or it
might have to retrieve the resource content to recalculate a patch,
or it might have to fail the operation.
Other HTTP status codes can also be used under the appropriate Other HTTP status codes can also be used under the appropriate
circumstances. circumstances.
The entity body of error responses SHOULD contain enough information The entity body of error responses SHOULD contain enough information
to communicate the nature of the error to the client. The content- to communicate the nature of the error to the client. The content-
type of the response entity can vary across implementations. type of the response entity can vary across implementations.
3. Advertising Support in OPTIONS 3. Advertising Support in OPTIONS
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security considerations for PUT ([RFC2616], Section 9.6). These security considerations for PUT ([RFC2616], Section 9.6). These
include authorizing requests (possibly through access control and/or include authorizing requests (possibly through access control and/or
authentication) and ensuring that data is not corrupted through authentication) and ensuring that data is not corrupted through
transport errors or through accidental overwrites. Whatever transport errors or through accidental overwrites. Whatever
mechanisms are used for PUT can be used for PATCH as well. The mechanisms are used for PUT can be used for PATCH as well. The
following considerations apply specially to PATCH. following considerations apply specially to PATCH.
A document that is patched might be more likely to be corrupted than A document that is patched might be more likely to be corrupted than
a document that is overridden in entirety, but that concern can be a document that is overridden in entirety, but that concern can be
addressed through the use of mechanisms such as conditional requests addressed through the use of mechanisms such as conditional requests
using ETags and the If-Match request header. using ETags and the If-Match request header as described in
Section 2. If a PATCH request fails, the client can issue a GET
request to the resource to see what state it is in. In some cases,
the client might be able to check the contents of the resource to see
if the PATCH request can be resent, but in other cases the attempt
will just fail and/or a user will have to verify intent. In the case
of a failure of the underlying transport channel, where a PATCH
response is not received before the channel fails or some other
timeout happens, the client might have to issue a GET request to see
whether the request was applied. The client might want to ensure
that the GET request bypasses caches using mechanisms described in
HTTP specifications (see for example Section 13.1.6 of [RFC2616]).
Sometimes an HTTP intermediary might try to detect viruses being sent Sometimes an HTTP intermediary might try to detect viruses being sent
via HTTP by checking the body of the PUT/POST request or GET via HTTP by checking the body of the PUT/POST request or GET
response. The PATCH method complicates such watch-keeping because response. The PATCH method complicates such watch-keeping because
neither the source document nor the patch document might be a virus, neither the source document nor the patch document might be a virus,
yet the result could be. This security consideration is not yet the result could be. This security consideration is not
materially different from those already introduced by byte-range materially different from those already introduced by byte-range
downloads, downloading patch documents, uploading zipped (compressed) downloads, downloading patch documents, uploading zipped (compressed)
files and so on. files and so on.
skipping to change at page 9, line 23 skipping to change at page 10, line 4
Appendix A. Acknowledgements Appendix A. Acknowledgements
PATCH is not a new concept, it first appeared in HTTP in drafts of PATCH is not a new concept, it first appeared in HTTP in drafts of
version 1.1 written by Roy Fielding and Henrik Frystyk and also version 1.1 written by Roy Fielding and Henrik Frystyk and also
appears in Section 19.6.1.1 of RFC 2068. appears in Section 19.6.1.1 of RFC 2068.
Thanks to Adam Roach, Chris Sharp, Julian Reschke, Geoff Clemm, Scott Thanks to Adam Roach, Chris Sharp, Julian Reschke, Geoff Clemm, Scott
Lawrence, Jeffrey Mogul, Roy Fielding, Greg Stein, Jim Luther, Alex Lawrence, Jeffrey Mogul, Roy Fielding, Greg Stein, Jim Luther, Alex
Rousskov, Jamie Lokier, Joe Hildebrand, Mark Nottingham, Michael Rousskov, Jamie Lokier, Joe Hildebrand, Mark Nottingham, Michael
Balloni and Cyrus Daboo for review and advice on this document. Balloni, Cyrus Daboo, Brian Carpenter, John Klensin, Eliot Lear and
SM for review and advice on this document.
Appendix B. Changes Appendix B. Changes
B.1. Changes from -00 B.1. Changes from -00
OPTIONS support: removed "Patch" header definition and used Allow and OPTIONS support: removed "Patch" header definition and used Allow and
new "Accept-Patch" headers instead. new "Accept-Patch" headers instead.
Supported delta encodings: removed vcdiff and diffe as these do not Supported delta encodings: removed vcdiff and diffe as these do not
have defined MIME types and did not seem to be strongly desired. have defined MIME types and did not seem to be strongly desired.
skipping to change at page 13, line 24 skipping to change at page 14, line 7
-- it is not absolutely required -- it is not absolutely required
Clarified how server can indicate that a PATCH response body is Clarified how server can indicate that a PATCH response body is
cachable as a resource representation. cachable as a resource representation.
Removed suggestion that PATCH side-effects might be specified in the Removed suggestion that PATCH side-effects might be specified in the
patch document specification -- this implied that side-effects could patch document specification -- this implied that side-effects could
exclusively be determined that way, but in fact side-effects are exclusively be determined that way, but in fact side-effects are
often determined by the server unilaterally. often determined by the server unilaterally.
B.16. Changes from -15
Clarifications on how conflicting PATCH requests can be avoided, and
why not all use cases necessarily involve conflict
Added Content-Location to example response, so the ETag would be
legit
Expanded security considerations on avoiding collisions, recovering
from possible (unknown) collisions
Very slight reordering of paragraphs in section 2, for better flow
Clarified that the concurrent-modification status response is
optional for servers, and explained what clients can do with that
response
Updated text describing conflicting modifications: when 412 is used,
vs 409
Appendix C. Notes to RFC Editor Appendix C. Notes to RFC Editor
The RFC Editor should remove this section and the Changes section. The RFC Editor should remove this section and the Changes section.
Authors' Addresses Authors' Addresses
Lisa Dusseault Lisa Dusseault
Linden Lab Linden Lab
945 Battery Street 945 Battery Street
San Francisco, CA 94111 San Francisco, CA 94111
 End of changes. 24 change blocks. 
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