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Network Working Group                                          A. Newton
Internet-Draft                                                      ARIN
Intended status: Standards Track                         August 28, 2014
Expires: March 1, 2015


              A Language for Rules Describing JSON Content
                   draft-newton-json-content-rules-02

Abstract

   This document describes a language useful for documenting the
   expected content of JSON structures found in specifications using
   JSON.

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 March 1, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   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
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   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.





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1.  Introduction

   The goal of this document is to provide a way to document the
   expected content of data expressed in JSON [RFC4627] format.  That
   is, the primary purpose of this document is to specify a means for
   one person to communicate with another person the expected nature of
   a JSON data structure in a method more concise than prose.  The
   programmatic validation of a JSON data structure against content
   rules is a lesser goal of this document, though such a practice is
   useful in both the writing of specifications and the communications
   of programs.

   Unlike JSON Schema, this language is not JSON though the syntax
   described here is "JSON-like" (a comparison with JSON Schema can be
   found in Appendix A and a "real world" example can be found in
   Appendix B).  A specialized syntax is used to reduce the tedium in
   reading and writing rules as the complexity describing allowable
   content is often more involved than most of the actual content.
   Figure 2 is an example of this language describing the JSON of
   Figure 1.

   Example JSON lifted from RFC 4627

   [
       {
          "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"
       }
   ]

                                 Figure 1




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   Rules describing Figure 1

   root [
       2*2{
           "precision" : string,
           "Latitude" : float,
           "Longitude" : float,
           "Address" : string,
           "City" : string,
           "State" : string,
           "Zip" : string,
           "Country" : string
       }
   ]

                                 Figure 2

   The JSON Content Rules are of five types:

   o  value rules

   o  member rules

   o  array rules

   o  object rules

   o  group rules

   Each rule has two components, a rule name and a rule definition.
   Anywhere in a rule definition where a rule name is allowed, another
   rule definition may be used.

   This is an example of a value rule:

      v1 : integer 0..3

   It specifies a rule named "v1" that has a definition of ": integer
   0..3" (value rule definitions begin with a ':' character).  This
   defines values of type "v1" to be integers in the range 0 to 3
   (minimum value of 0, maximum value of 3).  Value rules can define the
   limits of JSON values, such as stating that numbers must fall into a
   certain range or that strings must be formatted according to certain
   patterns or standards (i.e.  URIs, phone numbers, etc...).

   Member rules specify JSON object members.  The following example
   member rule states that the rules name is 'm1' with a value defined
   by the 'v1' value rule:



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      m1 "m1name" v1

   Since rule names can be substituted by rule definitions, this member
   rule can also be written as follows:

      m1 "m1name" : integer 0..3

   Object rules are composed of member rules, since JSON objects are
   composed of members.  Object rules can specify members that are
   mandatory, optional, and even choices between members.  In this
   example, the rule 'o1' defines an object that must contain a member
   as defined by member rule 'm1' and optionally a member defined by the
   rule 'm2':

      o1 { m1, ?m2 }

   Finally, array rules are composed of value and object rules.  Like
   object rules, array rules can specify the cardinality of the contents
   of an array.  The following array rule defines an array that must
   contain value rule 'v1' and zero or more objects as defined by rule
   'o1':

      a1 [ v1, *o1 ]

   Putting it all together, Figure 4 describes the JSON in Figure 3.

   Example JSON shamelessly lifted from RFC 4627

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

                                 Figure 3








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   Rules describing Figure 3

   width_v : integer 0..1280
   height_v : integer 0..1024

   width "width" width_v
   height "height" height_v

   thumbnail "thumbnail" {
       width, height, "Url" : uri
   }

   image "Image" {
       width, height, "Title" : string,
       thumbnail, "IDs" [ *: integer ]
   }

   root { image }

                                 Figure 4

   The rules from Figure 4 can be written more compactly (see Figure 5).

   Compact rules describing Figure 3

   width "width" : integer 0..1280
   height "height" : integer 0..1024

   root {
       "Image" {
           width, height, "Title" :string,
           "thumbnail" { width, height, "Url" :uri },
           "IDs" [ *:integer ]
       }
   }

                                 Figure 5

2.  Lines and Comments

   There is no statement terminator and therefore no need for a line
   continuation syntax.  Blank lines are allowed.

   Comments are very similar to comments in ABNF [RFC4234].  They start
   with a semi-colon (';') and continue to the end of the line.






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3.  Rules

   Rules are composed of two parts, a rule name and a rule definition.
   Rule names allow a rule definition to be referenced easily by a name.
   With the exception of value rules, rule definitions refer to other
   rules using the rule names of other appropriate types of rules.
   Because of this, it is also possible to use a rule definition of the
   appropriate type where a rule name of that type would be appropriate.

   The type of rule to use in a rule definition, either directly or by
   reference of a name, depends on the type of rule being defined and
   fall along the structure of allowable JSON grammar:

   o  Since a member of a JSON object can contain a "primitive value",
      an array, or an object, member rules can be composed of value
      rules, array rules, and object rules.

   o  JSON objects are composed of members, so object rules can only be
      composed of member rules.

   o  Finally, as JSON arrays may contain other arrays, objects, and
      values, array rules may be composed of value rules, object rules,
      and array rules.

   A fifth rule type, group rules, exist to help reference a collection
   of rules.

   Rule names must start with an alphabetic character (a-z,A-Z) and must
   contain only alphabetic characters, numeric characters, the hyphen
   character ('-') and the underscore character ('_').  Rule names must
   not be used more than once.

3.1.  Value Rules

   Value rules define content for JSON values.  JSON allows values to be
   objects, arrays, numbers, booleans, strings, and null.  Arrays and
   objects are handled by the array and object rules, and the value
   rules define the rest.

3.1.1.  Numbers, Booleans and Null

   The rules for booleans and null are the simplest and take the
   following forms:

      rule_name : boolean

      rule_name : null




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   Rules for numbers can specify the number as either an integer or
   floating point number and may specify a range:

      rule_name : integer n..m

      rule_name : float n..m

   where n is the minimum allowable value of the number and m is the
   maximum allowable value of the number.  The range doesn't have to be
   given, but if it is given either the minimum, maximum, or both are
   required.  If the minimum is not given then the minimum is considered
   to be the minimum number value possible to represent in JSON.
   Likewise, if the maximum is not given then the maximum is considered
   to be the maximum number value possible to represent in JSON.

3.1.2.  Strings

   String values may be specified generically as:

      rule_name : string

   However, the content of strings can be narrowed in the following
   ways:

   Regular Expression:   A rule can state that a string must match a
      regular expression by giving the regular expression after the
      string literal:

         rule_name : string /regex/

   URIs:   A rule can state that a string must be a URI [RFC3986]:

         rule_name : uri

      URIs can also be scoped further by providing the literals 'full'
      or 'relative' to indicate that the URI must be either a full URI
      or a relative URI:

         rule_name : uri relative

      And the scheme of the URI can also be specified:

         rule_name : uri full http

      Neither the scheme nor the full/relative literals need to be
      specified, and neither need to be specified together.





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   IP Addresses:   Narrowing the content of strings down to IP addresses
      can be done with either the 'ip4' (see [RFC1166]) or 'ip6' (see
      [RFC5952]) literals:

         rule_name : ip4

         rule_name : ip6

   Domain Names:   Fully qualified A-label and U-label domain names can
      be specified with the 'fqdn' and 'idn' literals:

         rule_name : fqdn

         rule_name : idn

   Dates and Times:   Dates and times are specified using the ABNF rules
      from RFC 3339 [RFC3339] as literals:

         rule_name : date-time

         rule_name : full-date

         rule_name : full-time

   Email Addresses:   A string can be scoped to the syntax of email
      addresses using the literal 'email' followed by an optional
      conformance level:

         rule_name : email 2822

         rule_name : email 5322

      Conformance levels are specified with the literal '2822'
      signifying RFC 2822 [RFC2822] conformance or '5322' signifying RFC
      5322 [RFC5322] conformance.

   Phone Numbers:   Strings conforming to E.123 phone number format can
      be specified as follows:

         rule_name : phone

   Base 64:   Strings containing base 64 data, as described by RFC 4648
      [RFC4648], can be specified as follows:

         rule_name : base64






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3.2.  Member Rules

   Member rules are the simplest of the rules and define members of JSON
   objects.  Member rules follow the format:

      rule_name "member_name" target_rule_name

   where rule_name is the name of the rule being defined, member_name
   (in quotes) is the name of the JSON object member, and
   target_rule_name is a reference to a value rule, array rule, or
   object rule specifying the allowable content of the JSON object
   member.

   Since rule names in rule definitions may be substituted for rule
   definitions, member rules may also be written in this form:

      rule_name "member_rule" target_rule_definition

   The following is an example:

      location_uri "locationURI" : uri

3.3.  Object Rules

   Object rules define the allowable members of a JSON object.  Their
   rule definitions are composed of member rules and group rules.  They
   take the following form:

      rule_name { member_rule_1, member_rule_2 }

   The following rule example defines an object composed of two member
   rules:

      response { location_uri, status_code }

   Given the general rule that where a rule name is found a rule
   definition of the appropriate type may be used, the above example
   might also be written:

      response { "locationUri" : uri, "statusCode" : integer }

   Rules given in the rule definition of an object rule do not imply
   order.  Given the example object rule above both

      { "locationUri" : "http://example.com", "statusCode" : 200 }

   and




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      { "statusCode" : 200, "locationUri" : "http://example.com" }

   are JSON objects that match the rule.

   Member rules or member rule definitions may not be repeated in the
   rule definition of an object rule.  However, a member of an object
   can be marked as optional if the member rule defining it is preceded
   by the question mark ('?') character.  In the following example, the
   location_uri member is optional while the status_code member is
   required to be in the defined object:

      response { ?location_uri, status_code }

   An object rule can also define the choice between members by placing
   the forward slash ('/') character between two member rules.  In the
   following example, the object being defined can have either a
   location_uri member or content_type member and must have a
   status_code member:

      response { location_uri / content_type, status_code }

   Finally, the specification of a member of an object can be
   conditioned upon the the specification of another member of that
   object by placing the ampersand ('&') character between two member
   rules.  Using this syntax, the member defined by the second rule is
   only allowed in the object if the member defined by the first rule is
   given.  Or in other words, the appearance of the second member
   depends upon the appearance of the first member.  In the following
   example, the object defined can have a referrer_uri so long as
   location_uri is also present:

      response { location_uri & referrer_uri }

3.4.  Array Rules

   Array rules define the allowable content of JSON arrays.  Their rule
   definitions are composed of value rules, object rules, group rules,
   and other array rules and have the following form:

      rulename [ target_rule_name_1, target_rule_name_2 ]

   The following example defines an array where element 1 is defined by
   the width_value rule and element 2 is defined by the height_value
   rule:

      size [ width_value, height_value ]





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   Unlike object rules, order is implied by the array rule definition.
   That is, the first rule referenced or defined within an array rule
   specifies that the first element of the array will match that rule,
   the second rule given with the array rule specifies that the second
   element of the array will match that rule, and so on.

   Take for example the following array rule definition:

      person [ : string, : integer ]

   This JSON array matches the above rule:

      [ "Bob Smurd", 24 ]

   while this one does not:

      [ 24, "Bob Smurd" ]

   As with object rules, the forward slash character ('/') can be used
   to indicate a choice between two elements.  Take for example the
   following rules:

      name_value : string

      age_value : integer

      birthdate_value : date-time

      person [ name_value, age_value / birthdate_vale ]

   which would validate

      [ "Bob Smurd", 24 ]

   or

      [ "Bob Smurd", "1988-04-12T23:20:50.52Z" ]

   Repetition of array values may also be specified by preceding a rule
   with an asterisk ('*') character surrounded by the lower bound and
   upper bound of the repetition (e.g. "0*1").  The following rules
   define an array that has between one and three strings:

      child_value : string

      children [ 1*3 child_value ]





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   Both the lower bound and the upper bound are optional.  If lower
   bound is not given then it is assumed to be zero.  If the upper bound
   is not given then it is assumed to be infinity.  The following
   example defines an array with an infinite number of child_value
   defined strings:

      children [ * child_value ]

3.5.  Group Rules

   Unlike the other types of rules, group rules have no direct tie with
   JSON syntax.  Group rules simply group together other rules.  They
   take the form:

      rule_name ( target_rule_1, target_rule_2 )

   Group rule definitions and any nesting of group rule definitions,
   must conform to the allowable set of rules of the rule containing
   them.  A group rule referenced inside of an array rule may not
   contain a member rule since member rules are not allowed in array
   rules directly.  Likewise, a group rule referenced inside an object
   rule must only contain member rules, and once group rules used in an
   object rule are fully dereferenced there must be no duplicate member
   rules as member rules in object rules are required to be unique.

   Take for example the following rules:

      child_1 "first_child" : string

      child_2 "second_child" : string

      child_3 "third_child" : string

      child_4 "fourth_child" : string

      first_two_children ( child_1, child_2 )

      second_two_children ( child_3, child_4 )

      the_children { first_two_children, second_two_children }

   These rules describe a JSON object that might look like this:

      { "first_child":"greg", "second_child":"marsha",
      "third_child":"bobby", "fourth_child":"jan" }






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   Groups can also be used with the choice and dependency syntax in
   member rules.  Here the object can either have first_two_children or
   second_two_children:

      the_children { first_two_children / second_two_children }

   and here the object can have second_two_children only if
   first_two_children are given:

      the_children { first_two_children & second_two_children }

3.6.  Any Value and Any Member

   It is possible to specify that a value can be of any type allowable
   by JSON using the any value rule.  This is done with the 'any'
   literal in a value rule:

      rule_name : any

   However, unlike other value rules which define primitive data types,
   this rule defines a value of any kind, either primitive (null,
   boolean, number, string), object, or array.

   Use of the any value rule in arrays can be used with repetition to
   define arrays that may contain any value:

      any_value : any

      array_of_any [ *any_value ]

   Specifying any object member name in a member rule with the any
   member rule is done by pre-pending a carat character ('^') to an
   empty member name (that is, ^"" signifies any member name).  This has
   the following form:

      rule_name ^"" target_rule_name

   As an example, the following defines an object member with any name
   that has a value that is a string:

      user_data ^"" : string

   Usage of the any member rule must still satisfy the criteria that all
   member names of an object be unique.

   Constructing an object member of any name with any type would
   therefore take the form:




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      rule_name ^"" : any

   Unlike other types of member rules, it is possible to use repetition
   with the any member rule in an object rule.  The repetition syntax
   and semantics are the same as the repetition syntax and semantics of
   repetition with array rules.  The following example rules define an
   object that may contain any number of members where each member may
   have any value.

      any_member ^"" : any

      object_of_anything { *any_member }

   Use of the repetition of any member rules must satisfy the criteria
   that all member names of an object be unique.

3.7.  A Root Rule

   In some contexts it is necessary that there be a rule that defines
   the outer most JSON object or array, or if thought of as an inverted
   object tree the structure at the very top.  If in a collection of
   rules there is no rule explicitly specified for this purpose and a
   rule named "root" is given, it can be assumed to be the outer most
   JSON structure or the root of an object/array tree.  If a rule is
   explicitly specified other than "root" and there exists a rule named
   "root", that rule name holds no special meaning.

4.  Directives

   Directives change the interpretation of a collection of rules.  They
   begin with a hash character ('#') and are terminated by the end of a
   line.  They take the following form:

      # directive_name

4.1.  ignore-unknown-members

   This directive specifies that any member of any object which has not
   been specified should be ignored.  Ignored object members may have a
   value of any type.  This directive cannot be used in any collection
   of rules that has an any member rule.

4.2.  language-compatible-members

   This directive specifies that every member name of every object,
   either explicitly defined or specified via an any member rule or the
   ignore-unknown-members directive must be a name compatible with
   programming languages.  The intent is to specify object member names



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   that may be promoted to first-order object attributes or methods in
   an API.  The following ABNF describes the restrictions upon the
   member names:

   ABNF for programming language compatible JSON names


   name = ALPHA *( ALPHA / DIGIT / "_" )


                                 Figure 6

4.3.  all-members-optional

   This directive specifies that every member of every object is not
   required.  This directive effectively pre-pends a '?' to every member
   rule in every object rule.

5.  Formal Syntax

   The following ABNF describes the syntax for JSON Content Rules.

grammar         = 1*(rule / directive) *c-wsp

rule            = rulename definition
definition      = *c-wsp ( value-rule / member-rule / array-rule / object-rule / group-rule )

; rulenames must be unique, and may not be a reserved word
rulename        = *c-wsp ALPHA *(ALPHA / DIGIT / "-" / "_")

; Adapted from the ABNF for JSON, RFC 4627 s 2.4
float           = [ "-" ] int [ frac ] [ exp ]
integer         = [ "-" ] int [ exp ]
exp             = ( "e" / "E" ) [ "+" / "-" ] 1*DIGIT
frac            = "." 1*DIGIT
int             = "0" / ( %x31-39 *DIGIT )

; The regex-char rule allows for any sequence of characters, including
; whitespace and newlines, with backslash only allowed before either
; a forward or a backslash.
regex-char      = %x21-2E / %x30-5D / %x5E-7E / WSP /
                  CR / LF / "\/" / "\\"

; uri-scheme from RFC 3986
uri-scope       = *c-wsp ( "relative" / "full" )
uri-scheme      = *c-wsp ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )

boolean-type    = "boolean"



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null-type       = "null"
integer-type    = "integer" [ 1*c-wsp integer ".." integer ]
float-type      = "float"   [ 1*c-wsp float   ".." float   ]
string-type     = "string"  [ *c-wsp "/" *regex-char "/" ]
uri-type        = "uri"     [ uri-scope ] [ uri-scheme ]
ip-type         = "ip4" / "ip6"
dns-type        = "fqdn" / "idn"
date-type       = "date-time" / "full-date" / "full-time"
email-type      = "email" [ *c-wsp ( "2822" / "5322" ) ]
phone-type      = "phone"
base64-type     = "base64"
any-type        = "any"

value-rule      = ":" *c-wsp type-rule
type-rule       = boolean-type /
                  null-type /
                  integer-type /
                  float-type /
                  string-type /
                  uri-type /
                  ip-type /
                  dns-type /
                  date-type /
                  email-type /
                  phone-type /
                  base64-type /
                  any-type

inline-rule     = *c-wsp ( rulename / definition )

; The defintion of a JSON string, from RFC 4627 s 2
json-name       = %x20-21 / %x23-5B / %x5D-10FFFF / "\" (
                    %x22 /      ; "  u+0022
                    %x5C /      ; \  u+005C
                    %x2F /      ; /  u+002F
                    %x62 /      ; BS u+0008
                    %x66 /      ; FF u+000C
                    %x6E /      ; LF u+000A
                    %x72 /      ; CR u+000D
                    %x74 /      ; HT u+0009
                    ( %x75 4HEXDIG ) ) ; uXXXX u+XXXX

member-rule     = ( ( "^" %x22.22 ) / ( %x22 *json-name %x22 ) ) inline-rule

object-rule     = "{" [ object-member *( *c-wsp ( "," / "/" / "&" ) object-member ) ] *c-wsp "}"

object-member   = *c-wsp ["?"] ( rulename / member-rule / group-rule )




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array-rule      = "[" [ array-member *( *c-wsp "," array-member ) ] *c-wsp "]"

array-count     = *c-wsp [ [int] "*" [int] *c-wsp ]
array-member    = array-count ( rulename / value-rule / object-rule / group-rule )
                  [ *c-wsp "/" array-member ]

group-rule      = "(" [ group-member *( *c-wsp "," group-member) ] *c-wsp ")"

group-member    =  ["?"] inline-rule [ *c-wsp ( "/" / "&" ) group-member ]

directive       = *c-wsp "#" *( VCHAR / WSP / %x7F-10FFFF ) EOL

; Taken from the ABNF for ABNF (RFC 4627 section 4) and slightly adapted
; newlines in a c-wsp do not need whitespace at the start of a newline
; to form a valid continuation line, and EOL might not be a full CRLF
c-wsp           = WSP / c-nl
c-nl            = comment / EOL
comment         =  ";" *(WSP / VCHAR) EOL
EOL             = 1*( CR / LF )

; core rules
ALPHA          =  %x41-5A / %x61-7A   ; A-Z / a-z
CR             =  %x0D
DIGIT          =  %x30-39
HEXDIG         =  DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
LF             =  %x0A
VCHAR          =  %x21-7E
WSP            =  SP / HTAB
SP             =  %x20
HTAB           =  %x09

                          JSON Content Rules ABNF

6.  Acknowledgements

   Many thanks to Byron Ellacott for providing the ABNF in Section 5.

7.  Normative References

   [RFC1166]  Kirkpatrick, S., Stahl, M., and M. Recker, "Internet
              numbers", RFC 1166, July 1990.

   [RFC2822]  Resnick, P., "Internet Message Format", RFC 2822, April
              2001.

   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the
              Internet: Timestamps", RFC 3339, July 2002.




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   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

   [RFC4234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              October 2008.

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952, August 2010.

Appendix A.  Comparison with JSON Schema

   This section compares this specification, JSON Content Rules, with
   JSON Schema using examples.

A.1.  Example 1 from RFC 4627


























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   Example JSON lifted from RFC 4627

   [
       {
          "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"
       }
   ]

   JSON Content Rules

   root [
       2*2{
           "precision" : string,
           "Latitude" : float,
           "Longitude" : float,
           "Address" : string,
           "City" : string,
           "State" : string,
           "Zip" : string,
           "Country" : string
       }
   ]












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   JSON Schema

  {
      "type": "array",
      "items": [
          {
              "type": "object",
              "properties": {
                  "precision": { "type": "string", "required": "true" },
                  "Latitude": { "type": "number", "required": "true" },
                  "Longitude": { "type": "number", "required": "true" },
                  "Address" : { "type": "string", "required": "true" },
                  "City" : { "type": "string", "required": "true" },
                  "State" : { "type" : "string", "required": "true" },
                  "Zip" : { "type" : "string", "required": "true" },
                  "Country" : { "type" : "string", "required": "true" }
              }
          }
      ],
      "minItems" : 2,
      "maxItems" : 2
  }

A.2.  Example 2 from RFC 4627

   Example JSON shamelessly lifted from RFC 4627

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











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   JSON Content Rules

   width "width" : integer 0..1280
   height "height" : integer 0..1024

   root {
       "Image" {
           width, height, "Title" :string,
           "thumbnail" { width, height, "Url" :uri },
           "IDs" [ *:integer ]
       }
   }

   JSON Schema

   {
       "type" : "object",
       "properties" : {
           "Image": {
               "type" : "object",
               "properties" : {
                   "Width" : {
                       "type" : "integer",
                       "minimum" : 0,
                       "maximum" : 1280,
                       "required" : "true"
                   }
                   "Height" : {
                       "type" : "integer",
                       "minimum" : 0,
                       "maximum" : 1024,
                       "required" : "true"
                   }
                   "Title" : { "type": "string" },
                   "Thumbnail" : {
                       "type" : "object",
                       "properties" : {
                           "Url" : {
                               "type" : "string",
                               "format" : "uri",
                               "required" : "true"
                           },
                           "Width" : {
                               "type" : "integer",
                               "minimum" : 0,
                               "maximum" : 1280,
                               "required" : "true"
                           },



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                           "Height" : {
                               "type" : "integer",
                               "minimum" : 0,
                               "maximum" : 1280,
                               "required" : "true"
                           }
                       }
                   },
                   "IDs" : {
                       "type":"array",
                       "items":[ { "type": "integer" } ],
                       "required" : "true"
                   }
               }
           }
       }
   }

Appendix B.  A "Real World" Exmaple

   The following example is taken from draft-ietf-weirds-json-response-
   00.  It describes the entity object (Section 4), the nameserver
   object (Section 5) and many of the other sub-structures used in
   objects defined in other sections of that draft.

   JSON Content Rules for nameserver and entity from draft-ietf-weirds-
   json-response

   # all-members-optional
   # ignore-unknown-members
   # language-compatible-members

   ; the nameserver object
   ; models nameserver host information
   ; this often referred to as 'host' object too
   nameserver {

     ; the host name of the name server
     "name" : fqdn,

     ; the ip addresses of the nameserver
     "ipAddresses" [ *( :ip4 / :ip6 ) ],

     common
   }

   ; the entity object
   ; This object object represents the information of organizations,



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   ; corporations, governments, non-profits, clubs, individual persons,
   ; and informal groups of people.
   entity {

     ; the names by which the entity is commonly known
     "names" [ *:string ],

     ; the roles this entity has with any containing object
     "roles" [ *:string ],

     ; the place where the person, org, etc... receives postal mail
     ; THIS IS NOT LOCATION
     "postalAddress" [ *:string ],

     ; electronic mailboxes where the person, org, etc...
     ; receives messages
     "emails" [ *:email 2822 ],

     ; phones where the person, org, etc... receives
     ; telephonic communication
     "phones" {
         "office" [ *:phone ], ; office phones
         "fax" [ *:phone ],    ; facsilime machines
         "mobile" [ *:phone ]  ; cell phones and the like
     },

     common
   }

   ; The members "handle", "status", "remarks", "uris", "port43",
   ; "sponsoredBy", "resoldBy", "registrationBy", "registrationDate",
   ; "lastChangedDate", and "lastChangedBy" are used in many objects
   common (

     ; a registry-unique identifier
     "handle" : string,

     ; an array of status values
     "status" [ *:string ],

     ; an array of strings, each containing comments about the object
     "remarks" [ *:string ].

     ; an array of uri objects
     ; "type" referrs to the application of the URI
     ; "uri" is the uri
     "uris" [
       *{ "type" : string, "uri" : uri }



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     ],

     ; a string containing the fully-qualified host name of the
     ; WHOIS [RFC3912] server where the object instance may be found
     "port43" : fqdn,

     ; a string containing an identifier of the party
     ; through which the registration was made, such as an IANA approved
     ; registrar
     "sponsoredBy" : string,

     ; a string containing an identifier of the party
     ; originating the registration of the object.
     "resoldBy" : string,

     ; a string containing an identifier of the party
     ; responsible for the registration of the object
     "registrationBy" : string,

     ; the date the object was registered
     "registrationDate" : date-time,

     ; the date of last change made to the object
     "lastChangedDate" : date-time,

     ; a string containing an identifier of the party
     ; responsible for the last change made to the registration
     "lastChangedBy" : string
   )


Appendix C.  Design Notes

C.1.  Member Uniqueness

   JSON does not disallow non-unique object member names ( in other
   words, it allows non-unique object member names ) but strongly
   advises against the use of non-unique object member names.  Many JSON
   implementations use hash-indexed maps to represent JSON objects,
   where the object's member names are the key of the hash index.  Non-
   uniqueness would break such implementations or result in the value of
   the last member given overwriting the value of all previous members
   of the same name.

   Therefore, allowing non-unique object member names would be bad
   practice.  For this reason, this specification does not accommodate
   the need for non-unique object member names.




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C.2.  Member Order

   JSON gives awkward guidance regarding ordering of object member
   names.  However, many JSON implementations use hash-indexed maps to
   represent JSON objects, where the object's member names are the key
   of the hash index.  Though it is possible, usually these maps have no
   explicit order as the only index is the hash.

   Therefore, this specification does not provide a means to imply order
   of object member names.

C.3.  Group Syntax for Arrays and Objects

   It is possible to create a separate group syntax for array rules vs
   object rules, since allowable group rule content is determined by the
   containing rule.  For instance, while the syntax for groups in
   objects could have been "( blah blah )", syntax for groups in arrays
   could have been "< blah blah >".  That may be more distinctive and
   allow the formal syntax parser to handle rule content validity, but
   the added extra syntax appeared to hurt readability.  There is only
   so many enclosure characters a person should reasonably be required
   to know, and adding yet another did not seem prudent.

C.4.  Inspiration

   The original approach to this problem was to find a concise way to
   describe JSON data structures; to do for JSON what RelaxNG compact
   syntax does for XML.  The syntax itself hopefully has a JSON-ness or
   a JSON feel to it.  And a good bit of inspiration came from ABNF.

C.5.  Changelog

   From -00 to -01

   1.  Added ABNF.  Thanks Byron Ellacott.

   2.  Added section about root rules.

   3.  Other minor edits.

   From -01 to -02

   1.  Other minor edits.

   2.  Added the Possible Future Changes section.

   3.  Mostly a keep-alive version.




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C.6.  Possible Future Changes

   The following is a list of possible modifications and additions to
   this specification.

   1.  Reduction of some of the built-in string patterns.  Specifically,
       only one email pattern and getting rid of the URI full vs
       relative.

   2.  A way to specify a string can come from an enumerated list of
       strings other than with a regex.

   3.  A method for referencing other collections of rules.

   4.  A rule or modification to an existing rule that allows a value to
       be either a primitive JSON value or an array of those primitive
       JSON values.

Author's Address

   Andrew Lee Newton
   American Registry for Internet Numbers
   3635 Concorde Parkway
   Chantilly, VA  20151
   US

   Email: andy@arin.net
   URI:   http://www.arin.net























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