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Versions: (draft-pbryan-json-patch) 00 01 02 03 04 05 06 07 08 09 10 RFC 6902

Applications Area Working Group                            P. Bryan, Ed.
Internet-Draft                                            Salesforce.com
Intended status: Informational                        M. Nottingham, Ed.
Expires: March 21, 2013                               September 17, 2012


                               JSON Patch
                    draft-ietf-appsawg-json-patch-04

Abstract

   JSON Patch defines the media type "application/json-patch", a JSON
   document structure for expressing a sequence of operations 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 March 21, 2013.

Copyright Notice

   Copyright (c) 2012 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.  Document Structure . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Operations . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     4.1.  add  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     4.2.  remove . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     4.3.  replace  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.4.  move . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.5.  copy . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.6.  test . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Error Handling . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     9.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Examples  . . . . . . . . . . . . . . . . . . . . . . 10
     A.1.  Adding an Object Member  . . . . . . . . . . . . . . . . . 10
     A.2.  Adding an Array Element  . . . . . . . . . . . . . . . . . 10
     A.3.  Removing an Object Member  . . . . . . . . . . . . . . . . 11
     A.4.  Removing an Array Element  . . . . . . . . . . . . . . . . 11
     A.5.  Replacing a Value  . . . . . . . . . . . . . . . . . . . . 12
     A.6.  Moving a Value . . . . . . . . . . . . . . . . . . . . . . 12
     A.7.  Moving an Array Element  . . . . . . . . . . . . . . . . . 13
     A.8.  Testing a Value: Success . . . . . . . . . . . . . . . . . 13
     A.9.  Testing a Value: Error . . . . . . . . . . . . . . . . . . 14
     A.10. Adding a nested Member Object  . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14




















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1.  Introduction

   JavaScript Object Notation (JSON) [RFC4627] is a common format for
   the exchange and storage of structured data.  HTTP PATCH [RFC5789]
   extends the Hypertext Transfer Protocol (HTTP) [RFC2616] with a
   method to perform partial modifications to resources.

   The JSON Patch media type "application/json-patch" is a JSON document
   structure for expressing a sequence of operations to apply to a
   target JSON document, suitable for use with the HTTP PATCH method.


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.  Document Structure

   A JSON Patch document contains a JSON array of objects.  Each object
   contains a single operation to apply to the target JSON document.

   An example JSON Patch document:

   [
       { "test": "/a/b/c", "value": "foo" },
       { "remove": "/a/b/c" },
       { "add": "/a/b/c", "value": [ "foo", "bar" ] },
       { "replace": "/a/b/c", "value": 42 },
       { "move": "/a/b/c", "to": "/a/b/d" },
       { "copy": "/a/b/c", "to": "/a/b/e" }
   ]

   Evaluation of a JSON Patch document begins with a target JSON
   document.  Operations are applied sequentially in the order they
   appear in the array.  Each operation in the sequence is applied to
   the target document; the resulting document becomes the target of the
   next operation.  Evaluation continues until all operations are
   successfully applied or an error condition is encountered.


4.  Operations

   The operation to perform is expressed in a member of the operation
   object.  The name of the operation member is one of: "add", "remove",
   "replace", "move", "copy" or "test".



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   The member value is a string containing a [JSON-Pointer] value that
   references the location within the target document to perform the
   operation.  It is an error condition if an operation object contains
   no recognized operation member or more than one operation member.

4.1.  add

   The "add" operation adds a new value at the specified location in the
   target document.  The location must reference one of: the root of the
   target document, a member to add to an existing object, or an element
   to add to an existing array.  The operation object contains a "value"
   member that specifies the value to be added.

   Example:

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

   If the location references the root of the target document or a
   member of an existing object, it is an error condition if a value at
   the specified location already exists.

   If the location references an element of an existing array, any
   elements at or above the specified index are shifted one position to
   the right.  It is an error condition if the specified index is
   greater than the number of elements in the array.

   Note that this operation will, in common use, contain a JSON Pointer
   that does not resolve to an existing value in the target document.
   As such, the pointer's error handling algorithm is invoked.  This
   specification defines the error handling algorithm for "add" pointers
   to explicitly ignore the error and perform the operation as
   specified.

   It is an error condition if the "value" member is not present.

4.2.  remove

   The "remove" operation removes the value at the specified location in
   the target document.

   Example:

   { "remove": "/a/b/c" }

   If removing an element from an array, any elements above the
   specified index are shifted one position to the left.

   It is an error condition if a value at the specified location does



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   not exist.

4.3.  replace

   The "replace" operation replaces the value at the specified location
   in the target document with a new value.  The operation object
   contains a "value" member that specifies the replacement value.

   Example:

   { "replace": "/a/b/c", "value": 42 }

   This operation is functionally identical to expressing a "remove"
   operation for a value, followed immediately by an "add" operation at
   the same location with the replacement value.

   It is an error condition if a value at the specified location does
   not exist.

   It is an error condition if the "value" member is not present.

4.4.  move

   The "move" operation removes the value at one location and adds it to
   another location in the target document.

   The operation object contains a "to" member, a string containing a
   JSON Pointer value that references the location in the target
   document to add the value to.  This location must reference one of:
   the member to add to an existing object, or an element to add to an
   existing array.

   Example:

   { "move": "/a/b/c", "to": "/a/b/d" }

   This operation is functionally identical to expressing a "remove"
   operation, followed immediately by an "add" operation at the new
   location with the value that was just removed.  Moving a value to its
   current location can be safely ignored.

   If the location in the "to" member references a member of an existing
   object in the target document, it is an error condition if a value at
   the specified location already exists (unless "move" and "to" specify
   the same object, which has no effect).

   If the location in the "to" member references an element of an
   existing array, any elements at or above the specified index are



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   shifted one position to the right.  It is an error condition if the
   specified index is greater than the number of elements in the array.

   It is an error condition if the "to" member is not present.

4.5.  copy

   The "copy" operation copies the value at one location to another
   location in the target document.

   The operation object contains a "to" member, a string containing a
   JSON Pointer value that references the location in the target
   document to add the value to.  This location must reference one of:
   the member to add to an existing object, or an element to add to an
   existing array.

   Example:

   { "copy": "/a/b/c", "to": "/a/b/e" }

   If the location in the "to" member references a member of an existing
   object in the target document, it is an error condition if a value at
   the specified location already exists.

   If the location in the "to" member references an element of an
   existing array, any elements at or above the specified index are
   shifted one position to the right.  It is an error condition if the
   specified index is greater than the number of elements in the array.

   It is an error condition if the "to" member is not present.

4.6.  test

   The "test" operation tests that a value at the specified location in
   the target document is equal to a specified value.  The operation
   object contains a "value" member that specifies the value to test
   for.

   Here, "equal" means that the target and specified values are of the
   same JSON type, and considered equal by the following rules for that
   type:

   o  strings: are considered equal if, after unescaping any sequence(s)
      in both strings starting with a reverse solidus, they contain the
      same number of Unicode characters and their code points are
      position-wise equal.





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   o  numbers: are considered equal if subtracting one from the other
      results in 0.

   o  arrays: are considered equal if they contain the same number of
      values, and each value can be considered equal to the value at the
      corresponding position in the other array.

   o  objects: are considered equal if they contain the same number of
      members, and each member can be considered equal to a member in
      the other object, by comparing their keys as strings, and values
      using this list of type-specific rules.

   o  literals (false, true and null): are considered equal if they are
      the same.

   Note that this is a logical comparison; e.g., whitespace between the
   member values of an array is not significant.

   Also, note that ordering of the serialisation of object members is
   not significant.

   Example:

   { "test": "/a/b/c", "value": "foo" }

   It is an error condition if the value at the specified location is
   not equal to the specified value.

   If the value is not specified, the test is only for presence, not
   value.

   For example:

   { "test": "/a/b/c" }

   merely tests that the indicated structure is present in the target
   document.


5.  Error Handling

   If an error condition occurs, evaluation of the JSON Patch document
   SHOULD terminate and application of the entire patch document SHALL
   NOT be deemed successful.  Note that as per [RFC5789], when used with
   the PATCH HTTP method, it is atomic.

   Therefore, the following patch would result in no changes being made
   to the document at all (because the "test" operation results in an



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   error).

   [
    {"replace": "/a/b/c", "value": 42},
    {"test": "/a/b/c", "value": "C"}
   ]


6.  IANA Considerations

   The Internet media type for a JSON Patch document is application/
   json-patch.

   Type name:  application

   Subtype name:  json-patch

   Required parameters:  none

   Optional parameters:   none

   Encoding considerations:  binary

   Security considerations:
      See Security Considerations in section 7.

   Interoperability considerations:  N/A

   Published specification:
      [this memo]

   Applications that use this media type:
      Applications that manipulate JSON documents.

   Additional information:

      Magic number(s):  N/A

      File extension(s):  .json-patch

      Macintosh file type code(s):  TEXT

   Person & email address to contact for further information:
      Paul C. Bryan <pbryan@anode.ca>







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   Intended usage:  COMMON

   Restrictions on usage:  none

   Author:  Paul C. Bryan <pbryan@anode.ca>

   Change controller:  IETF


7.  Security Considerations

   This specification has the same security considerations as JSON
   [RFC4627] and [JSON-Pointer].


8.  Acknowledgements

   The following individuals contributed ideas, feedback and wording to
   this specification:

      Mike Acar, Mike Amundsen, Paul Davis, Murray S. Kucherawy, Dean
      Landolt, Randall Leeds, Julian Reschke, James Snell, Eli Stevens.

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


9.  References

9.1.  Normative References

   [JSON-Pointer]
              Bryan, P. and K. Zyp, "JSON Pointer",
              draft-ietf-appsawg-json-pointer-04 (work in progress),
              March 2012.

   [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.

9.2.  Informative References

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.




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   [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

A.1.  Adding an Object Member

   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:





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

A.3.  Removing an Object Member

   An example target JSON document:

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

   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" ]
   }







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A.5.  Replacing a Value

   An example target JSON document:

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

   A JSON Patch document:

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

   The resulting JSON document:

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

A.6.  Moving a Value

   An example target JSON document:

   {
       "foo": {
           "bar": "baz",
           "waldo": "fred"
       }
       "qux": {
           "corge": "grault"
       }
   }

   A JSON Patch document:

   [
       { "move": "/foo/waldo", to: "/qux/thud" }
   ]

   The resulting JSON document:








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   {
       "foo": {
           "bar": "baz"
       }
       "qux": {
           "corge": "grault",
           "thud": "fred"
       }
   }

A.7.  Moving an Array Element

   An example target JSON document:

   {
       "foo": [ "all", "grass", "cows", "eat" ]
   }

   A JSON Patch document:

   [
       { "move": "/foo/1", "to": "/foo/3" }
   ]

   The resulting JSON document:

   {
       "foo": [ "all", "cows", "eat", "grass" ]
   }

A.8.  Testing a Value: Success

   An example target JSON document:

   {
       "baz": "qux",
       "foo": [ "a", 2, "c" ]
   }

   A JSON Patch document that will result in successful evaluation:

   [
       { "test": "/baz", "value": "qux" },
       { "test": "/foo/1", "value": 2 }
   ]






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A.9.  Testing a Value: Error

   An example target JSON document:

   {
       "baz": "qux"
   }

   A JSON Patch document that will result in an error condition:

   [
       { "test": "/baz", "value": "bar" }
   ]

A.10.  Adding a nested Member Object

   An example target JSON document:

   {
      "foo": "bar"
   }

   A JSON Patch document:

   [
     { "add": "/child", "value": { "grandchild": { } } }
   ]

   The resulting JSON document:

   {
     "foo": "bar",
     "child": {
       "grandchild": {
       }
     }
   }


Authors' Addresses

   Paul C. Bryan (editor)
   Salesforce.com

   Phone: +1 604 783 1481
   Email: pbryan@anode.ca





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   Mark Nottingham (editor)

   Email: mnot@mnot.net
















































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