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Versions: 00 01 02 03 04 draft-ietf-appsawg-json-patch

Internet Engineering Task Force                            P. Bryan, Ed.
Internet-Draft                                        ForgeRock US, Inc.
Intended status: Informational                              June 9, 2011
Expires: December 11, 2011


A JSON Media Type for Describing Partial Modifications to JSON Documents
                       draft-pbryan-json-patch-01

Abstract

   JSON (JavaScript Object Notation) Patch defines the media type
   "application/patch+json", a JSON-based document structure for
   specifying partial modifications to apply to a JSON document.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 11, 2011.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Motivations . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Patch Object Structure  . . . . . . . . . . . . . . . . . . . . 3
   5.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     5.1.  add . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     5.2.  remove  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     5.3.  replace . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 5
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . . . 5
     A.1.  Adding an Object Property . . . . . . . . . . . . . . . . . 6
     A.2.  Adding an Array Element . . . . . . . . . . . . . . . . . . 6
     A.3.  Removing an Object Property . . . . . . . . . . . . . . . . 6
     A.4.  Removing an Array Element . . . . . . . . . . . . . . . . . 7
     A.5.  Replacing a Value . . . . . . . . . . . . . . . . . . . . . 7
   Appendix B.  Changelog  . . . . . . . . . . . . . . . . . . . . . . 8
   Appendix C.  Open Issues  . . . . . . . . . . . . . . . . . . . . . 8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8

























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1.  Introduction

   This Internet-Draft proposes the JSON-Patch media type "application/
   patch+json", a JSON structure for specifying partial modifications to
   apply to a JSON document.


2.  Conventions

   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 RFC 2119 [RFC2119].


3.  Motivations

   JavaScript Object Notation (JSON) [RFC4627] is a popular format for
   the storage and transmission of structured data.  As a result,
   numerous web service APIs support the JSON media type.

   The HTTP PATCH [RFC5789] specification extends HTTP with a new method
   to perform partial modifications to resources.  A JSON-based patch
   document type is required to modify JSON documents using this method.


4.  Patch Object Structure

   A JSON Patch document is a JSON document that contains an array of
   objects.  Each object contains a patch operation to apply to a target
   JSON document.

   A sample JSON Patch document:

   [
     { "remove": "/a/b/c" },
     { "add": "/a/b/c", "value": "foo" },
     { "replace": "/a/b/c", "value": "bar" }
   ]

   Patch operations are applied sequentially in the order they appear in
   the array.  After a patch operation has been applied, the resulting
   JSON document becomes the target for the next patch operation.  This
   process repeats until all patches are successfully applied.


5.  Operations

   Operations are specified in the name of a property in the patch



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   operation object, with that property's value being a string
   containing the [JSON Pointer] that references the node to be
   affected.

5.1.  add

   Adds a new value into an object or array.  The value to be added to
   the object or array is specified in the "value" property.

   If adding to an object, it is an error condition if the property to
   be added in the object already exists.

   If adding to an array, any elements at or above the specified index
   are shifted one position to the right (i.e. indexes are incremented).
   It is an error condition if the addition would result in sparse
   allocation of any array elements.

5.2.  remove

   Removes the value specified by the JSON Pointer value.

   If removing an element from an array, any elements above the
   specified index are shifted one position to the left (i.e. indexes
   are decremented).

   It is an error condition if the value to be removed does not exist.

5.3.  replace

   Replaces the value referenced by the JSON Pointer with a new value.
   Syntacically equivalent to performing a "remove" operation, followed
   immediately by an "add" operation.  The value to be replaced is
   specified in the "value" property.

   It is an error condition if the value to be replaced does not exist.


6.  Error Handling

   In the event of an error condition, evaluation of the JSON Patch
   document ceases.  Enforcing safety and/or idempotency of a JSON Patch
   document is specified by and enforced by the implementation.


7.  Acknowledgements

   The structure of a JSON Patch document was informed by the XML Patch
   document [RFC5261] specification.



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8.  IANA Considerations

   The proposed MIME media type for the JSON Patch document is
   "application/patch+json".

   Type name: application

   Subtype name: patch+json

   Required parameters: none

   Optional parameters: none


9.  Security Considerations

   This specification is based on the JSON format, therefore has the
   same security considerations as [RFC4627].


10.  References

10.1.  Normative References

   [JSON Pointer]
              Bryan, P. and K. Zyp, "JSON Pointer", June 2011, <http://
              tools.ietf.org/html/draft-pbryan-zyp-json-pointer-00>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

10.2.  Informative References

   [RFC5261]  Urpalainen, J., "An Extensible Markup Language (XML) Patch
              Operations Framework Utilizing XML Path Language (XPath)
              Selectors", RFC 5261, September 2008.

   [RFC5789]  Dusseault, L. and J. Snell, "PATCH Method for HTTP",
              RFC 5789, March 2010.


Appendix A.  Examples






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A.1.  Adding an Object Property

   An example target JSON document:

   {
     "foo": "bar"
   }

   A JSON Patch document:

   [
     { "add": "/baz", "value": "qux" }
   ]

   The resulting JSON document:

   {
     "baz": "qux",
     "foo": "bar"
   }

A.2.  Adding an Array Element

   An example target JSON document:

   {
     "foo": [ "bar", "baz" ]
   }

   A JSON Patch document:

   [
     { "add": "/foo/1", "value": "qux" }
   ]

   The resulting JSON document:

   {
     "foo": [ "bar", "qux", "baz" ]
   }

A.3.  Removing an Object Property

   An example target JSON document:

   {
     "baz": "qux",
     "foo": "bar"



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   }

   A JSON Patch document:

   [
     { "remove": "/baz" }
   ]

   The resulting JSON document:

   {
     "foo": "bar"
   }

A.4.  Removing an Array Element

   An example target JSON document:

   {
     "foo": [ "bar", "qux", "baz" ]
   }

   A JSON Patch document:

   [
     { "remove": "/foo/1" }
   ]

   The resulting JSON document:

   {
     "foo": ["bar", "baz"]
   }

A.5.  Replacing a Value

   An example target JSON document:

   {
     "baz": "qux",
     "foo": "bar"
   }

   A JSON Patch document:

   [
       { "replace": "/baz", "value": "boo" }
     ]



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   }

   The resulting JSON document:

   {
     "baz": "boo",
     "foo": "bar"
   }


Appendix B.  Changelog

   Draft 00

   o  Initial draft.

   Draft 01

   o  Switched from JSONPath to JSON Pointer to reference nodes.

   o  Removed "op"; property name now contains operation to perform.

   o  Removed "element"; JSON Pointer now contains target node.

   o  Added "replace" operation to decrease operation verbosity.


Appendix C.  Open Issues

   Interest has been expressed in conforming to a uniform PUT/DELETE
   interface, and providing for idempotent and non-idempotent operations
   within the patch document format.


Author's Address

   Paul C. Bryan (editor)
   ForgeRock US, Inc.
   201 NE Park Plaza Drive Suite 196
   Vancouver, WA  98684
   USA

   Phone: +1 604 783 1481
   Email: paul.bryan@forgerock.com







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