



Applications Area Working Group                            P. Bryan, Ed.
Internet-Draft                                            Salesforce.com
Intended status: Standards Track                      M. Nottingham, Ed.
Expires: August 17, 2013                                          Akamai
                                                       February 13, 2013


                               JSON Patch
                    draft-ietf-appsawg-json-patch-10

Abstract

   JSON Patch defines a JSON document structure for expressing a
   sequence of operations to apply to a JavaScript Object Notation
   (JSON) document, suitable for use with the HTTP PATCH method.  The
   "application/json-patch" media type is used to identify such patch
   documents.

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 August 17, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.












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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Document Structure  . . . . . . . . . . . . . . . . . . . . .   3
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  add . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  remove  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.3.  replace . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.4.  move  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.5.  copy  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.6.  test  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  11
     A.1.  Adding an Object Member . . . . . . . . . . . . . . . . .  11
     A.2.  Adding an Array Element . . . . . . . . . . . . . . . . .  11
     A.3.  Removing an Object Member . . . . . . . . . . . . . . . .  12
     A.4.  Removing an Array Element . . . . . . . . . . . . . . . .  12
     A.5.  Replacing a Value . . . . . . . . . . . . . . . . . . . .  13
     A.6.  Moving a Value  . . . . . . . . . . . . . . . . . . . . .  13
     A.7.  Moving an Array Element . . . . . . . . . . . . . . . . .  14
     A.8.  Testing a Value: Success  . . . . . . . . . . . . . . . .  14
     A.9.  Testing a Value: Error  . . . . . . . . . . . . . . . . .  15
     A.10. Adding a nested Member Object . . . . . . . . . . . . . .  15
     A.11. Ignoring Unrecognized Elements  . . . . . . . . . . . . .  15
     A.12. Adding to a Non-existant Target . . . . . . . . . . . . .  16
     A.13. Invalid JSON Patch Document . . . . . . . . . . . . . . .  16
     A.14. ~ Escape Ordering . . . . . . . . . . . . . . . . . . . .  17
     A.15. Comparing Strings and Numbers . . . . . . . . . . . . . .  17
     A.16. Adding an Array Value . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18




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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.

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

   This format is also potentially useful in other cases where necessary
   to make partial updates to a JSON document, or to a data structure
   that has similar constraints (i.e., they can be serialised as an
   object or an array using the JSON grammar).

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].

   See Section 5 for information about handling errors.

3.  Document Structure

   A JSON Patch document is a JSON [RFC4627] document that represents an
   array of objects.  Each object represents a single operation to be
   applied to the target JSON document.

   An example JSON Patch document, transferred in a HTTP PATCH request:

   PATCH /my/data HTTP/1.1
   Host: example.org
   Content-Length: 326
   Content-Type: application/json-patch
   If-Match: "abc123"

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





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   Evaluation of a JSON Patch document begins against 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

   Operation objects MUST have exactly one "op" member, whose value
   indicates the operation to perform.  Its value MUST be one of "add",
   "remove", "replace", "move", "copy" or "test"; other values are
   errors.  The semantics of each is defined below.

   Additionally, operation objects MUST have exactly one "path" member.
   That member's value is a string containing a [JSON-Pointer] value
   that references a location within the target document (the "target
   location") where the operation is performed.

   The meanings of other members of operation objects are defined by
   operation (see the subsections below).  Members that are not
   explicitly defined for the operation in question MUST be ignored
   (i.e., the operation will complete as if the undefined member did not
   appear in the object).

   Note that the ordering of members in JSON objects is not significant;
   therefore, the following operation objects are equivalent:

   { "op": "add", "path": "/a/b/c", "value": "foo" }
   { "path": "/a/b/c", "op": "add", "value": "foo" }
   { "value": "foo", "path": "/a/b/c", "op": "add" }


   Operations are applied to the data structures represented by a JSON
   document; i.e., after any unescaping (see [RFC4627], Section 2.5)
   takes place.

4.1.  add

   The "add" operation performs the following function, depending upon
   what the target location references:

   o  If the target location specifies an array index, a new value is
      inserted into the array at the specified index.

   o  If the target location specifies an object member that does not
      already exist, a new member is added to the object.




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   o  If the target location specifies an object member that does exist,
      that member's value is replaced.

   The operation object MUST contain a "value" member whose content
   specifies the value to be added.

   For example:

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


   When the operation is applied, the target location MUST reference one
   of:

   o  The root of the target document - whereupon the specified value
      becomes the entire content of the target document.

   o  A member to add to an existing object - whereupon the supplied
      value is added to that object at the indicated location.  If the
      member already exists, it is replaced by the specified value.

   o  An element to add to an existing array - whereupon the supplied
      value is added to the array at the indicated location.  Any
      elements at or above the specified index are shifted one position
      to the right.  The specified index MUST NOT be greater than the
      number of elements in the array.  If the "-" character is used to
      index the end of the array (see [JSON-Pointer]), this has the
      effect of appending the value to the array.

   Because this operation is designed to add to existing objects and
   arrays, its target location will often not exist.  Although the
   pointer's error handling algorithm will thus be invoked, this
   specification defines the error handling behaviour for "add" pointers
   to ignore that error and add the value as specified.

   However, the object itself or an array containing it does need to
   exist, and it remains an error for that not to be the case.  For
   example, an "add" with a target location of "/a/b" starting with this
   document:

   { "a": { "foo": 1 } }


   is not an error, because "a" exists, and "b" will be added to its
   value.  It is an error in this document:

   { "q": { "bar": 2 } }




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   because "a" does not exist.

4.2.  remove

   The "remove" operation removes the value at the target location.

   The target location MUST exist for the operation to be successful.

   For example:

   { "op": "remove", "path": "/a/b/c" }


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

4.3.  replace

   The "replace" operation replaces the value at the target location
   with a new value.  The operation object MUST contain a "value" member
   whose content specifies the replacement value.

   The target location MUST exist for the operation to be successful.

   For example:

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


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

4.4.  move

   The "move" operation removes the value at a specified location and
   adds it to the target location.

   The operation object MUST contain a "from" member, a string
   containing a JSON Pointer value that references the location in the
   target document to move the value from.

   The "from" location MUST exist for the operation to be successful.

   For example:

   { "op": "move", "from": "/a/b/c", "path": "/a/b/d" }




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   This operation is functionally identical to a "remove" operation on
   the "from" location, followed immediately by an "add" operation at
   the target location with the value that was just removed.

   The "from" location MUST NOT be a proper prefix of the "path"
   location; i.e., a location cannot be moved into one of its children.

4.5.  copy

   The "copy" operation copies the value at a specified location to the
   target location.

   The operation object MUST contain a "from" member, a string
   containing a JSON Pointer value that references the location in the
   target document to copy the value from.

   The "from" location MUST exist for the operation to be successful.

   For example:

   { "op": "copy", "from": "/a/b/c", "path": "/a/b/e" }


   This operation is functionally identical to an "add" operation at the
   target location using the value specified in the "from" member.

4.6.  test

   The "test" operation tests that a value at the target location is
   equal to a specified value.

   The operation object MUST contain a "value" member that conveys the
   value to be compared to that at the target location.

   The target location MUST be equal to the "value" value for the
   operation to be considered successful.

   Here, "equal" means that the value at the target location and that
   conveyed by "value" are of the same JSON type, and considered equal
   by the following rules for that type:

   o  strings: are considered equal if they contain the same number of
      Unicode characters and their code points are position-wise equal.

   o  numbers: are considered equal if their values are numerically
      equal.





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   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, using this list of
      type-specific rules.

   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.

   For example:

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


5.  Error Handling

   If a normative requirement is violated by a JSON Patch document, or
   if an operation is not successful, evaluation of the JSON Patch
   document SHOULD terminate and application of the entire patch
   document SHALL NOT be deemed successful.

   See [RFC5789], Section 2.2 for considerations regarding handling
   errors when JSON Patch is used with the HTTP PATCH method, including
   suggested status codes to use to indicate various conditions.

   Note that the HTTP PATCH method is atomic, as per [RFC5789].
   Therefore, the following patch would result in no changes being made
   to the document at all (because the "test" operation results in an
   error).

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


6.  IANA Considerations




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   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:

         N/A

         .json-patch

         TEXT

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

   Intended usage:  COMMON

   Restrictions on usage:  none

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

   Change controller:  IETF









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7.  Security Considerations

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

   A few older Web browsers can be coerced into loading an arbitrary
   JSON document whose root is an array, leading to a situation where a
   JSON Patch document containing sensitive information could be exposed
   to attackers, even if access is authenticated.  This is known as a
   Cross-Site Request Forgery (CSRF) attack [CSRF].

   However, such browsers are not widely used ( estimated to comprise
   less than 1% of the market, at the time of writing).  Publishers who
   are nevertheless concerned about this attack are advised to avoid
   making such documents available with HTTP GET.

8.  Acknowledgements

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

      Mike Acar, Mike Amundsen, Cyrus Daboo, Paul Davis, Stefan Koegl,
      Murray S.  Kucherawy, Dean Landolt, Randall Leeds, James Manger,
      Julian Reschke, James Snell, Eli Stevens and Henry S.  Thompson.

   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., Zyp, K., and M. Nottingham, "JSON Pointer",
              draft-ietf-appsawg-json-pointer-07 (work in progress),
              November 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.









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9.2.  Informative References

   [CSRF]     Barth, A., Jackson, C., and J. Mitchell, "Robust Defenses
              for Cross-Site Request Forgery", 2012.

   [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.

   [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:

   [
     { "op": "add", "path": "/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:



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


   The resulting JSON document:

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


A.3.  Removing an Object Member

   An example target JSON document:

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


   A JSON Patch document:

   [
     { "op": "remove", "path": "/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:

   [
     { "op": "remove", "path": "/foo/1" }
   ]


   The resulting JSON document:




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


A.5.  Replacing a Value

   An example target JSON document:

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


   A JSON Patch document:

   [
     { "op": "replace", "path": "/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:







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   [
     { "op": "move", "from": "/foo/waldo", "path": "/qux/thud" }
   ]


   The resulting JSON document:

   {
     "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:

   [
     { "op": "move", "from": "/foo/1", "path": "/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:



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


A.9.  Testing a Value: Error

   An example target JSON document:

   { "baz": "qux" }


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

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


A.10.  Adding a nested Member Object

   An example target JSON document:

   { "foo": "bar" }


   A JSON Patch document:

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


   The resulting JSON document:

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


A.11.  Ignoring Unrecognized Elements

   An example target JSON document:



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   { "foo": "bar" }


   A JSON Patch document:

   [
     { "op": "add", "path": "/baz", "value": "qux", "xyz": 123 }
   ]


   The resulting JSON document:

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


A.12.  Adding to a Non-existant Target

   An example target JSON document:

   { "foo": "bar" }


   A JSON Patch document:

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


   This JSON Patch document, applied to the target JSON document above,
   would result in an error (therefore not being applied) because the
   "add" operation's target location that references neither the root of
   the document, nor a member of an existing object, nor a member of an
   existing array.

A.13.  Invalid JSON Patch Document

   A JSON Patch document:

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






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   This JSON Patch document cannot be treated as an "add" operation
   since there is a later "op":"remove" element.  JSON requires that
   object member names be unique with a "SHOULD" requirement, and there
   is no standard error handling for duplicates.

A.14.  ~ Escape Ordering

   An example target JSON document:

   {
     "/": 9,
     "~1": 10
   }


   A JSON Patch document:

   [
     {"op": "test", "path": "/~01", "value": 10}
   ]


   The resulting JSON document:

   {
     "/": 9,
     "~1": 10
   }


A.15.  Comparing Strings and Numbers

   An example target JSON document:

   {
     "/": 9,
     "~1": 10
   }


   A JSON Patch document:

   [
     {"op": "test", "path": "/~01", "value": "10"}
   ]






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   This results in an error, because the test fails; the document value
   is numeric, whereas the value tested for is a string.

A.16.  Adding an Array Value

   An example target JSON document:

   { "foo": ["bar"] }


   A JSON Patch document:

   [
     { "op": "add", "path": "/foo/-", "value": ["abc", "def"] }
   ]


   The resulting JSON document:

   { "foo": ["bar", ["abc", "def"]] }


Authors' Addresses

   Paul C. Bryan (editor)
   Salesforce.com

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


   Mark Nottingham (editor)
   Akamai

   Email: mnot@mnot.net















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