draft-ietf-appsawg-json-pointer-02.txt   draft-ietf-appsawg-json-pointer-03.txt 
Applications Area Working Group P. Bryan, Ed. Applications Area Working Group P. Bryan, Ed.
Internet-Draft ForgeRock Internet-Draft ForgeRock
Intended status: Informational K. Zyp Intended status: Informational K. Zyp
Expires: January 5, 2013 SitePen (USA) Expires: February 12, 2013 SitePen (USA)
M. Nottingham, Ed. M. Nottingham, Ed.
Rackspace Rackspace
July 4, 2012 August 11, 2012
JSON Pointer JSON Pointer
draft-ietf-appsawg-json-pointer-02 draft-ietf-appsawg-json-pointer-03
Abstract Abstract
JSON Pointer defines a string syntax for identifying a specific value JSON Pointer defines a string syntax for identifying a specific value
within a JSON document. within a JSON document.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 5, 2013. This Internet-Draft will expire on February 12, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. JSON String Representation . . . . . . . . . . . . . . . . . . 4 5. JSON String Representation . . . . . . . . . . . . . . . . . . 4
6. URI Fragment Identifier Representation . . . . . . . . . . . . 5 6. URI Fragment Identifier Representation . . . . . . . . . . . . 5
7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 5 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
11. Normative References . . . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
This specification defines JSON Pointer, a string syntax for This specification defines JSON Pointer, a string syntax for
identifying a specific value within a JavaScript Object Notation identifying a specific value within a JavaScript Object Notation
(JSON) [RFC4627] document. It is intended to be easily expressed in (JSON) [RFC4627] document. It is intended to be easily expressed in
JSON string values and Uniform Resource Identifier (URI) [RFC3986] JSON string values as well as Uniform Resource Identifier (URI)
fragment identifiers. [RFC3986] fragment identifiers.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
This specification expresses normative syntax rules using Augmented This specification expresses normative syntax rules using Augmented
Backus-Naur Form [RFC5234] (ABNF) notation. Backus-Naur Form [RFC5234] (ABNF) notation.
3. Syntax 3. Syntax
A JSON Pointer is a [Unicode] string containing a sequence of zero or A JSON Pointer is a [Unicode] string containing a sequence of zero or
more reference tokens, each prefixed by a '/' (%x2F) character. more reference tokens, each prefixed by a '/' (%x2F) character.
If a reference token contains '~' (%x7E) or '/' (%x2F) characters, If a reference token contains '~' (%x7E) or '/' (%x2F) characters,
they MUST be encoded as '~0' and '~1' respectively. they MUST be encoded as '~0' and '~1' respectively.
ABNF syntax: Its ABNF syntax is:
json-pointer = *( "/" reference-token ) json-pointer = *( "/" reference-token )
reference-token = *( unescaped / escaped ) reference-token = *( unescaped / escaped )
unescaped = %x00-2E / %x30-7D / %x7F-10FFFF unescaped = %x00-2E / %x30-7D / %x7F-10FFFF
escaped = "~" ( "0" / "1" ) escaped = "~" ( "0" / "1" )
It is an error condition if a JSON Pointer value does not conform to It is an error condition if a JSON Pointer value does not conform to
this syntax (see Section 7). this syntax (see Section 7).
4. Evaluation 4. Evaluation
Evaluation of a JSON Pointer begins with a reference to the root 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 of a JSON document and completes with a reference to some value
value within the document. Each reference token in the JSON Pointer within the document. Each reference token in the JSON Pointer is
is sequentially evaluated. sequentially evaluated.
Evaluation of each reference token begins by decoding any escaped Evaluation of each reference token begins by decoding any escaped
character sequence; this is performed by first transforming any character sequence; this is performed by first transforming any
occurrence of the sequence '~1' to '/', then transforming any occurrence of the sequence '~1' to '/', then transforming any
occurrence of the sequence '~0' to '~'. occurrence of the sequence '~0' to '~'.
The reference token then modifies which value is referenced according The reference token then modifies which value is referenced according
to the following scheme: to the following scheme:
If the currently referenced value is a JSON object, the new If the currently referenced value is a JSON object, the new
referenced value is the object member with the name (after referenced value is the object member with the name (after
unescaping any backslash escape sequences that can occur in a JSON unescaping any backslash escape sequences that can occur in a JSON
string) identified by the reference token. The member name is string) identified by the reference token. The member name is
equal to the token if it has the same number of Unicode characters equal to the token if it has the same number of Unicode characters
as token and their code points are position-wise equal. If a as token and their code points are position-wise equal. If a
referenced member name is not unique in an object, the member that referenced member name is not unique in an object, the member that
is referenced is undefined. is referenced is undefined, and evaluation fails (see below).
If the currently referenced value is a JSON array, the reference If the currently referenced value is a JSON array, the reference
token MUST contain characters that represent an unsigned base-10 token MUST contain characters that represent an unsigned base-10
integer value (possibly with leading zeros), and the new integer value (possibly with leading zeros), and the new
referenced value is the array element with the zero-based index referenced value is the array element with the zero-based index
identified by the token. identified by the token.
If a reference token is being evaluated against a JSON document, the If a reference token is being evaluated against a JSON document,
implementation MAY evaluate each token against a concrete value, and implementations will evaluate each token against the document's
terminate evaluation with an error condition if a evaluation fails to contents, and terminate evaluation with an error condition if it
resolve a concrete value (see Section 7). fails to resolve a concrete value for any of the JSON pointer's
reference tokens. See Section 7 for details.
5. JSON String Representation 5. JSON String Representation
A JSON Pointer can be represented in a JSON string value. Per A JSON Pointer can be represented in a JSON string value. Per
[RFC4627], section 2.5, all instances of quotation mark '"' (%x22), [RFC4627], section 2.5, all instances of quotation mark '"' (%x22),
reverse solidus '\' (%x5C) and control (%x00-1F) characters MUST be reverse solidus '\' (%x5C) and control (%x00-1F) characters MUST be
escaped. escaped.
For example, given the JSON document For example, given the JSON document
{ {
"foo": ["bar", "baz"], "foo": ["bar", "baz"],
"": 0 "": 0,
"a/b": 1, "a/b": 1,
"c%d": 2, "c%d": 2,
"e^f": 3, "e^f": 3,
"g|h": 4, "g|h": 4,
"i\\j": 5, "i\\j": 5,
"k\"l": 6, "k\"l": 6,
" ": 7, " ": 7,
"m~n": 8 "m~n": 8
} }
Then the following JSON strings evaluate to the accompanying values: Then the following JSON strings evaluate to the accompanying values:
"" // the whole document "" // the whole document
"/foo" ["bar", "baz"] "/foo" ["bar", "baz"]
"/foo/0" "bar" "/foo/0" "bar"
"/" 0 "/" 0
"/a~1b" 1 "/a~1b" 1
"/c%d" 2 "/c%d" 2
"/e^f" 3 "/e^f" 3
"/g|h" 4 "/g|h" 4
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"" // the whole document "" // the whole document
"/foo" ["bar", "baz"] "/foo" ["bar", "baz"]
"/foo/0" "bar" "/foo/0" "bar"
"/" 0 "/" 0
"/a~1b" 1 "/a~1b" 1
"/c%d" 2 "/c%d" 2
"/e^f" 3 "/e^f" 3
"/g|h" 4 "/g|h" 4
"/i\\j" 5 "/i\\j" 5
"/k\"l" 6 "/k\"l" 6
" " 7 "/ " 7
"m~0n" 8 "/m~0n" 8
6. URI Fragment Identifier Representation 6. URI Fragment Identifier Representation
A JSON Pointer can be represented in a URI fragment identifier. by A JSON Pointer can be represented in a URI fragment identifier. by
encoding it into octets, using UTF-8 [RFC3629], percent-encoding encoding it into octets, using UTF-8 [RFC3629], percent-encoding
those characters not allowed by the fragment rule in [RFC3986]. those characters not allowed by the fragment rule in [RFC3986].
Note that a given media type needs to nominate JSON Pointer as its
fragment identifier syntax explicitly (usually, in its registration
[RFC4288]); i.e., just because a document is JSON does not imply that
JSON Pointer can be used as its fragment identifier syntax.
Given the same example document as above, the following URI fragment Given the same example document as above, the following URI fragment
identifiers evaluate to the accompanying values: identifiers evaluate to the accompanying values:
# // the whole document # // the whole document
#/foo ["bar", "baz"] #/foo ["bar", "baz"]
#/foo/0 "bar" #/foo/0 "bar"
#/ 0 #/ 0
#/a~1b 1 #/a~1b 1
#/c%25d 2 #/c%25d 2
#/e%5Ef 3 #/e%5Ef 3
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This specification does not define how errors are handled; an This specification does not define how errors are handled; an
application of JSON Pointer SHOULD specify the impact and handling of application of JSON Pointer SHOULD specify the impact and handling of
each type of error. each type of error.
For example, some applications might stop pointer processing upon an For example, some applications might stop pointer processing upon an
error; others may attempt to recover from missing values by inserting error; others may attempt to recover from missing values by inserting
default ones. default ones.
8. IANA Considerations 8. IANA Considerations
TBD This document has no impact upon IANA.
9. Security Considerations 9. Security Considerations
A given JSON Pointer is not guaranteed to reference an actual JSON A given JSON Pointer is not guaranteed to reference an actual JSON
value. Implementations should be aware of this and take appropriate value. Implementations should be aware of this and take appropriate
precautions. precautions.
Note that JSON pointers can contain the NUL (Unicode U+0000) Note that JSON pointers can contain the NUL (Unicode U+0000)
character, which may not be representable in all programming character, which may not be representable in all programming
languages. languages.
10. Acknowledgements 10. Acknowledgements
The following individuals contributed ideas, feedback and wording to The following individuals contributed ideas, feedback and wording to
this specification: this specification:
Mike Acar, Carsten Bormann, Tim Bray, Jacob Davies, Martin J. Mike Acar, Carsten Bormann, Tim Bray, Jacob Davies, Martin J.
Duerst, Bjoern Hoehrmann, James H. Manger, Drew Perttula, Julian Duerst, Bjoern Hoehrmann, James H. Manger, Drew Perttula, Julian
Reschke. Reschke.
11. Normative References 11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
skipping to change at page 7, line 17 skipping to change at page 7, line 26
[RFC4627] Crockford, D., "The application/json Media Type for [RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006. JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[Unicode] The Unicode Consortium, "The Unicode Standard, Version [Unicode] The Unicode Consortium, "The Unicode Standard, Version
6.0", October 2011, 6.0", October 2011,
<http://www.unicode.org/versions/Unicode6.0.0/>. <http://www.unicode.org/versions/Unicode6.0.0/>.
11.2. Informative References
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
Authors' Addresses Authors' Addresses
Paul C. Bryan (editor) Paul C. Bryan (editor)
ForgeRock ForgeRock
Phone: +1 604 783 1481 Phone: +1 604 783 1481
Email: pbryan@anode.ca Email: pbryan@anode.ca
Kris Zyp Kris Zyp
SitePen (USA) SitePen (USA)
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