Applications Area Working Group P. Bryan, Ed.
Internet-Draft ForgeRock
Intended status: Informational K. Zyp
Expires: September 10, 2012 SitePen (USA)
March 9, 2012
JSON Pointer
draft-ietf-appsawg-json-pointer-01
Abstract
JSON Pointer defines a string syntax for identifying a specific value
within a JSON document.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 10, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. JSON String Representation . . . . . . . . . . . . . . . . . . 4
6. URI Fragment Identifier Representation . . . . . . . . . . . . 4
7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 4
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
11. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
This specification defines JSON Pointer, a string syntax for
identifying a specific value within a JavaScript Object Notation
(JSON) [RFC4627] text document. This syntax is intended to be easily
expressed in JSON string values and Uniform Resource Identifier (URI)
[RFC3986] fragment identifiers.
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 [RFC2119].
This specification expresses normative syntax rules using Augmented
Backus-Naur Form [RFC5234] (ABNF) notation.
3. Syntax
A JSON Pointer is a [Unicode] string containing a sequence of zero or
more reference tokens, each prefixed by a '/' (%x2F) character.
If a reference token contains '/' (%x2F) or '^' (%x5E) characters,
such characters MUST each be prefixed (escaped) with a '^' (%x5E)
character.
ABNF syntax:
json-pointer = *( "/" reference-token )
reference-token = *( unescaped / escaped )
unescaped = %x00-2E / %x30-5B / %x5D-10FFFF
escaped = "^" ( "/" / "^" )
It is an error condition if a JSON Pointer value does not conform to
this syntax.
4. Evaluation
Evaluation of a JSON Pointer begins with a reference to the root
value of a JSON text document and completes with a reference to some
value within the document. Each reference token in the JSON Pointer
is sequentially evaluated.
Evaluation of each reference token begins by unescaping any escaped
character sequence; this is performed by removing the '^' (escape)
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prefix. The reference token then modifies which value is referenced
according to the following scheme:
If the currently referenced value is a JSON object, the new
referenced value is the object member with the name identified by
the reference token. The member name is equal to the token if it
has the same number of Unicode characters as token and their
codepoints are positionwise equal. If a referenced member name is
not unique in an object, the member that is referenced is
undefined.
If the currently referenced value is a JSON array, the reference
token MUST contain characters that represent an unsigned base-10
integer value, and the new referenced value is the array element
with the zero-based index identified by the token.
If a reference token is being evaluated against a JSON document, the
implementation MAY evaluate each token against a concrete value, and
terminate evaluation with an error condition if a evaluation fails to
resolve a concrete value.
5. JSON String Representation
A JSON Pointer MAY be represented in a JSON string value. Per
[RFC4627], section 2.5, all instances of quotation mark '"' (%x22),
reverse solidus '\' (%x5C) and control (%x00-1F) characters MUST be
escaped.
6. URI Fragment Identifier Representation
A JSON Pointer MAY be represented in a URI fragment identifier. The
JSON pointer MUST be UTF-8 [RFC3629] encoded as octets; octets not in
the URI "unreserved" set SHOULD be percent-encoded, per [RFC3986],
section 2.5.
7. Error Handling
In the event of an error condition, evaluation of the JSON Pointer
fails to complete.
8. IANA Considerations
This document has no IANA actions.
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9. Security Considerations
A given JSON Pointer is not guaranteed to reference an actual JSON
value. Implementations should be aware of this and take appropriate
precautions.
10. Acknowledgements
The following individuals contributed ideas, feedback and wording,
which contributed to the content of this specification:
Mike Acar, Carsten Bormann, Tim Bray, Jacob Davies, Martin J.
Duerst, Bjoern Hoehrmann, James H. Manger, Mark Nottingham, Drew
Perttula, Julian Reschke.
11. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[Unicode] The Unicode Consortium, "The Unicode Standard, Version
6.0", October 2011,
<http://www.unicode.org/versions/Unicode6.0.0/>.
Appendix A. Examples
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The following examples illustrate the use of JSON Pointers in URI
fragments for a JSON text document located at
http://example.com/example.json, with the following value:
{
"foo": {
"bar": [ "element0", "element1" ],
"inner object": {
"baz": "qux"
}
}
http://example.com/example.json#
Resolves to the object value at the root of the JSON text
document.
http://example.com/example.json#/foo
Resolves to the object value of the "foo" member in the root
object.
http://example.com/example.json#/foo/inner%20object
Resolves to the object value of the "inner object" member in the
"foo" object value in the root object.
http://example.com/example.json#/foo/inner%20object/baz
Resolves to the string value "qux", which is the value of the
"baz" member in the "inner object" member in the "foo" member in
the root object.
http://example.com/example.json#/foo/bar/0
Resolves to the string value "element0", which is the first value
in the "bar" array in the "foo" member in the root object.
Authors' Addresses
Paul C. Bryan (editor)
ForgeRock
Phone: +1 604 783 1481
Email: pbryan@anode.ca
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Kris Zyp
SitePen (USA)
Phone: +1 650 968 8787
Email: kris@sitepen.com
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