Applications Area Working Group                            P. Bryan, Ed.
Internet-Draft                                            Salesforce.com
Intended status: Informational                        M. Nottingham, Ed.
Expires: March 21, 30, 2013                               September 17, 26, 2012

                               JSON Patch
                    draft-ietf-appsawg-json-patch-04
                    draft-ietf-appsawg-json-patch-05

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 21, 30, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 . . . . . . . . . . . . . . . . . . . . . . . . . .  3  4
     4.1.  add  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     4.2.  remove . . . . . . . . . . . . . . . . . . . . . . . . . .  4  5
     4.3.  replace  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.4.  move . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.5.  copy . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.6.  test . . . . . . . . . . . . . . . . . . . . . . . . . . .  6  7
   5.  Error Handling . . . . . . . . . . . . . . . . . . . . . . . .  7  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     9.2.  Informative References . . . . . . . . . . . . . . . . . .  9 10
   Appendix A.  Examples  . . . . . . . . . . . . . . . . . . . . . . 10
     A.1.  Adding an Object Member  . . . . . . . . . . . . . . . . . 10
     A.2.  Adding an Array Element  . . . . . . . . . . . . . . . . . 10 11
     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

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 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.

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 contains is a JSON [RFC4627] document whose root object
   is an array of objects.  Each object
   contains represents a single operation to apply
   be applied to the target JSON document.

   An example JSON Patch document:

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

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

   Additionally, operation objects MUST have exactly one "path" member,
   whose value MUST be 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 (the "target location").

   Other members of operation member. objects MUST be ignored, unless they are
   explicitly allowed by the definition of the operation.

   Note that the ordering of members in JSON objects is not significant;
   therefore, the following operations 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" }

4.1.  add

   The "add" operation adds a new value at the specified location in the target document. location.  The
   operation object MUST contain a "value" member that specifies the
   value to be added.

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

   o  the root of the target document,

   o  a member to add to an existing object, or

   o  an element to add to an existing array.  The operation object contains a "value"
   member that specifies the value to be added.

   Example:

   For example:

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

   If the target 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 MUST already exists.
   exist for the operation to be successful.

   If the target 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  The specified index is MUST NOT be greater than the
   number of elements in the array.

   Note that this operation will, in common use, contain have a JSON Pointer target location
   that does not resolve to an existing value value, resulting in the target document.
   As such, the
   pointer's error handling algorithm is being 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.

   The value at the specified location in MUST exist for the target document.

   Example: operation to
   be successful.

   For example:

   { "remove": "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.

   It is an error condition if a value at the specified location does
   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 MUST contain a "value" member
   that specifies the replacement value.

   Example:

   The value at the specified location MUST exist for the operation to
   be successful.

   For example:

   { "replace": "op": "replace", "path": "/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 the specified location and
   adds it to another location in the target document.

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

   The "to" location must MUST reference one of:

   o  the member to add to an existing object, or

   o  an element to add to an existing array.

   Example:

   For example:

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

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

   If the

   The location in the "to" member references MUST NOT reference 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 unless "move" and "to"
   specify the same object, which has no effect). effect.

   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  The specified index is MUST NOT be
   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 the specified location to
   another location in the target document.

   The operation object contains MUST contain 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 MUST reference one of:

   o  the member to add to an existing object, or

   o  an element to add to an existing array.

   Example:

   For example:

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

   If the

   The location in the "to" member references MUST NOT reference a member of an
   existing object in the target document, it is an error condition if a value at unless "move" and "to"
   specify the specified location already exists. 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
   shifted one position to the right.  It is an error condition if the  The specified index is MUST NOT be
   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 MUST contain a "value" member that specifies conveys the
   value to test
   for. be compared to that at the specified location.

   The value at the specified location MUST be equal to the specified
   value for the operation to be considered successful.

   Here, "equal" means that the target and value at the specified values location and the
   value 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, 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.

   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:

   For example:

   { "test": "op": "test", "path": "/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 a RFC2119 [RFC2119] requirement is violated by a JSON Patch
   document, or if an error condition occurs, 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 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 error).

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

   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, James Manger, 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.

   [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": "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:

   [
       { "add": "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:

   [
       { "remove": "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:

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

   [
       { "move": "op": "move", "path": "/foo/waldo", to: "/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:

   [
       { "move": "op": "move", "path": "/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": "op": "test", "path": "/baz", "value": "qux" },
       { "test": "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:

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

A.10.  Adding a nested Member Object

   An example target JSON document:

   {
      "foo": "bar"
   }

   A JSON Patch document:

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

   Mark Nottingham (editor)

   Email: mnot@mnot.net