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Versions: (draft-jsonorg-json) 00 01 02 03 04 RFC 4627

JavaScript Object Notation (JSON)                           D. Crockford
Internet Draft                                                  JSON.org
draft-crockford-jsonorg-json-04.txt                       February, 2006
Intended status: Informational
Expires: June 10, 2006

                    JavaScript Object Notation (JSON)

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   JavaScript Object Notation (JSON) is a light-weight, text-based,
   language-independent, data interchange format.  It was derived from
   the ECMAScript Programming Language Standard.  JSON defines a small
   set of formatting rules for the portable representation of structured
   data.

Conventions used in this document

   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].

   The grammatical rules in this document are to be interpreted as
   described in [RFC-4234].

1. Introduction

   JavaScript Object Notation (JSON) is a text format for the
   serialization of structured data.  It is derived from the object
   literals of JavaScript, as defined in the ECMAScript
   Programming Language Standard, Third Edition [ECMA].

   JSON can represent four primitive types (strings, numbers, booleans,
   and null) and two structured types (objects and arrays).

   A string is a sequence of zero or more Unicode characters [UNICODE].

   An object is an unordered collection of zero or more name/value
   pairs, where a name is a string, and a value is a string, number,
   boolean, null, object, or array.

   An array is an ordered sequence of zero or more values.

   The terms "object" and "array" come from the conventions of
   JavaScript.

   JSON's design goals were to be minimal, portable, textual, and a
   subset of JavaScript.

2. JSON Grammar

   A JSON text is a sequence of tokens.  The set of tokens includes six
   structural characters, strings, numbers, and three literal names.

   A JSON text is a serialized object or array.

      JSON-text = object / array

   These are the six structural characters:

      begin-array     = ws %x5B ws  ; [ left square bracket

      begin-object    = ws %x7B ws  ; { left curly bracket

      end-array       = ws %x5D ws  ; ] right square bracket

      end-object      = ws %x7D ws  ; } right curly bracket

      name-separator  = ws %x3A ws  ; : colon

      value-separator = ws %x2C ws  ; , comma

   Insignificant whitespace is allowed before or after any of the six
   structural characters.

      ws = *(
                %x20 /              ; Space
                %x09 /              ; Horizontal tab
                %x0A /              ; Line feed or New line
                %x0D                ; Carriage return
            )

   2.1. Values

      A JSON value MUST be a object, array, number, or string, or one of
      the three literal names:

         false
         null
         true

      The literal names MUST be in lower case.  No other literal names
      are allowed.

         value = false / null / true / object / array / number / string

         false = %x66.61.6c.73.65   ; false

         null  = %x6e.75.6c.6c      ; null

         true  = %x74.72.75.65      ; true

   2.2. Objects

      An object structure is represented as a pair of curly brackets
      surrounding zero or more name/value pairs (or members).  A name is
      a string.  A single colon comes after each name, separating the
      name from the value.  A single comma separates a value from a
      following name. The names within an object SHOULD be unique.

         object = begin-object [ member *( value-separator member ) ]
                  end-object

         member = string name-separator value

   2.3. Arrays

      An array structure is represented as square brackets surrounding
      zero or more values (or elements).  Elements are separated by
      commas.

         array = begin-array [ value *( value-separator value ) ]
                 end-array

   2.4. Numbers

      The representation of numbers is similar to that used in most
      programming languages.  A number contains an integer component
      which may be prefixed with an optional minus sign, which may be
      followed by a fraction part and/or an exponent part.

      Octal and hex forms are not allowed.  Leading zeros are not
      allowed.

      A fraction part is a decimal point followed by one or more digits.

      An exponent part begins with the letter E in upper or lower case,
      which may be followed by a plus or minus sign.  The E and optional
      sign are followed by one or more digits.

      Numeric values that cannot be represented as sequences of digits
      (such as Infinity and NaN) are not permitted.

         number = [ minus ] int [ frac ] [ exp ]

         decimal-point = %x2E       ; .

         digit1-9 = %x31-39         ; 1-9

         e = %x65 / %x45            ; e E

         exp = e [ minus / plus ] 1*DIGIT

         frac = decimal-point 1*DIGIT

         int = zero / ( digit1-9 *DIGIT )

         minus = %x2D               ; -

         plus = %x2B                ; +

         zero = %x30                ; 0

   2.5. Strings

      The representation of strings is similar to conventions used in
      the C family of programming languages.  A string begins and ends
      with quotation marks.  All Unicode characters may be placed within
      the quotation marks except for the characters which must be
      escaped: quotation mark, reverse solidus, and the control
      characters (U+0000 through U+001F).

      Any character may be escaped.  If the character is in the Basic
      Multilingual Plane (U+0000 through U+FFFF) then it may be
      represented as a six-character sequence: a reverse solidus
      followed by the lower case letter u followed by four hexadecimal
      digits which encode the character's code point.  The hexadecimal
      letters A though F can be in upper or lower case.  So, for
      example, a string containing only a single reverse solidus
      character may be represented as "\u005C".

      Alternatively, there are two-character sequence escape
      representations of some popular characters.  So, for example, a
      string containing only a single reverse solidus character may be
      represented more compactly as "\\".

      To escape an extended character that is not in the Basic
      Multilingual Plane, then the character is represented as a
      twelve-character sequence, encoding the UTF-16 surrogate pair.
      So, for example, a string containing only the G clef character
      (U+1D11E) may be represented as "\uD834\uDD1E".

         string = quotation-mark *char quotation-mark

         char = unescaped /
                escape (
                    %x22 /          ; "    quotation mark  U+0022
                    %x5C /          ; \    reverse solidus U+005C
                    %x2F /          ; /    solidus         U+002F
                    %x62 /          ; b    backspace       U+0008
                    %x66 /          ; f    form feed       U+000C
                    %x6E /          ; n    line feed       U+000A
                    %x72 /          ; r    carriage return U+000D
                    %x74 /          ; t    tab             U+0009
                    %x75 4HEXDIG )  ; uXXXX                U+XXXX

         escape = %x5C              ; \

         quotation-mark = %x22      ; "

         unescaped = %x20-21 / %x23-5B / %x5D-10FFFF

3. Encoding

   JSON text SHALL be encoded in Unicode. The default encoding is UTF-8.

   Since the first two characters of a JSON text will always be ASCII
   characters [RFC-0020], it is possible to determine if an octet stream
   is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking at the
   pattern of nulls in the first four octets.

           00 00 00 xx  UTF-32BE
           00 xx 00 xx  UTF-16BE
           xx 00 00 00  UTF-32LE
           xx 00 xx 00  UTF-16LE
           xx xx xx xx  UTF-8

4. Parsers

   A JSON parser transforms a JSON text into another representation.  A
   JSON parser MUST accept all texts that conform to the JSON grammar.
   A JSON parser MAY accept non-JSON forms or extensions.

   An implementation may set limits on the size of texts that it
   accepts.  An implementation may set limits on the maximum depth of
   nesting.  An implementation may set limits on the range of numbers.
   An implementation may set limits on the length and character contents
   of strings.

5. Generators

   A JSON generator produces JSON text.  The resulting text MUST
   strictly conform to the JSON grammar.

6. IANA Considerations

   The MIME media type for JSON text is application/json.

   Type name: text

   Subtype name: json

   Required parameters: n/a

   Optional parameters: n/a

   Encoding considerations: 8bit if UTF-8; binary if UTF-16 or UTF-32

      JSON may be represented using UTF-8, UTF-16 or UTF-32. When JSON
      is written in UTF-8, JSON is 8bit-compatible. When JSON is written
      in UTF-16 or UTF-32, the binary content-transfer-encoding must be
      used.

   Security considerations:

      Generally there are security issues with scripting languages.
      JSON is a subset of JavaScript, but it is a safe subset that
      excludes assignment and invocation.

      A JSON text can be safely passed into JavaScript's eval()
      function (which compiles and executes a string) if all of the
      characters not enclosed in strings are in the set of characters
      which form JSON tokens.  This can be quickly determined in
      JavaScript with two regular expressions and calls to the test and
      replace methods.

      var my_JSON_object = !(/[^,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/.test(
             text.replace(/"(\\.|[^"\\])*"/g, ''))) &&
         eval('(' + text + ')');

   Interoperability considerations: n/a

   Published specification: RFC-XXXX

   Applications that use this media type:

      JSON has been used to exchange data between applications written
      in all of these programming languages: ActionScript, C, C#,
      ColdFusion, Common Lisp, E, Erlang, Java, JavaScript, Lua,
      Objective CAML, Perl, PHP, Python, Rebol, Ruby, and Scheme.

   Additional information:

      Magic number(s): n/a
      File extension(s): .json
      Macintosh file type code(s): TEXT

   Person & email address to contact for further information:
      Douglas Crockford
      douglas@crockford.com

   Intended usage: COMMON

   Restrictions on usage: none

   Author:
      Douglas Crockford
      douglas@crockford.com

   Change controller:
      Douglas Crockford
      douglas@crockford.com

7. Security Considerations

   See Security considerations in Section 6.

8. Examples

   This is a JSON object:

   {
      "Image": {
          "Width":  800,
          "Height": 600,
          "Title":  "View from 15th Floor",
          "Thumbnail": {
              "Url":    "http://scd.mm-b1.yimg.com/image/481989943",
              "Height": 125,
              "Width":  "100"
          },
          "IDs": [116, 943, 234, 38793]
        }
   }

   Its Image member is an object whose Thumbnail member is an object
   and whose IDs member is an array of numbers.

   This is a JSON array containing two objects:

   [
      {
         "precision": "zip",
         "Latitude":  37.7668,
         "Longitude": -122.3959,
         "Address":   "",
         "City":      "SAN FRANCISCO",
         "State":     "CA",
         "Zip":       "94107",
         "Country":   "US"
      },
      {
         "precision": "zip",
         "Latitude":  37.371991,
         "Longitude": -122.026020,
         "Address":   "",
         "City":      "SUNNYVALE",
         "State":     "CA",
         "Zip":       "94085",
         "Country":   "US"
      }
   ]

9. References

9.1 Normative References

   [ECMA]     European Computer Manufacturers Association, "ECMAScript
              Language Specification 3rd Edition", December 1999,
              <http://www.ecma-international.org/publications/files/
                  ecma-st/ECMA-262.pdf>.

   [RFC-0020] Cerf, V., "ASCII format for Network Interchange",
              RFC 0020, October 16, 1969.

   [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.

   [RFC-4234] Crocker, D., "Augmented BNF for Syntax Specifications:
              ABNF", RFC 4234, October 2005.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard
              Version 4.0", 2003,
              <http://www.unicode.org/versions/Unicode4.1.0/>.

Author's Address

   Douglas Crockford
   JSON.org
   Contact Email: douglas@crockford.com

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