SION, a serialization format a little more expressive than JSON

This page introduces and describes SION, a data serialization format that addresses the shortcomings of JSON, arguably the most popular data serialization format today.

Because JSON is not expressive enough

SION is a data serialization format:

• Named after "Swift Interchangeable Object Notation". As JSON is originated from a {ECMA,Java}Script literal, SION is originated from a Swift literal.
  • but like JSON, it should not be considered acronym. It is a textual data format of its own and independent of programming languages.
• It can serialize anything JSON can. Plus
  • support Data - binary blobs
  • support Date
• non-String keys in Dictionary
  • Int and Double distinctively, not Number.
    • Therefore you can exchange 64-bit integers losslessly.
• Double can be expressed both in decimal and C99 Hexadecimal floating-point notation.
• NaN and ±Infinity are valid.
  • This is necessary for really interchangeable format. Suppose you want to send calculation results with errors.
• // comment is allowed!. // up to newline.
  • The lack of comment support of JSON definitely make it suck as a configuration file format.
• Roughly equivalent to MsgPack in terms of capability.
  • MsgPack is a binary serialization while SION is a text serialization.

Below is a table of a few notable serialization formats and capabilities.

Type	SION	MsgPack	JSON	Property List	Comment
Nil	✔︎	✔︎	✔︎	❌	plist: .binary only
Bool	✔︎	✔︎	✔︎	✔︎
Int	✔︎	✔︎	❌	✔︎	64bit
Double	✔︎	✔︎	✔︎	✔︎	JSON's Number
String	✔︎	✔︎	✔︎	✔︎	utf-8 encoded
Data	✔︎	✔︎	❌	✔︎	binary blob
Date	✔︎	✔︎	❌	✔︎	.timeIntervalSince1970 in Double
[Self]	✔︎	✔︎	✔︎	✔︎	aka Array
[String:Self]	✔︎	✔︎	✔︎	✔︎	aka Object, Map…
[Self:Self]	✔︎	✔︎	❌	❌	non-String keys
Ext	✔︎	✔︎	❌	❌	msgpack extension

Implementations

• Swift
  • swift-sion by dankogai
• Go
  • go-sion by mattn
• ECMAScript (aka JavaScript)
  • js-sion by dankogai
• Rust
  • sion-rs by pandaman64
• Python 3
  • py-sion by kamimura

Syntax

• ANTLR4(EBNF)
  • sion-antlr4 by kamimura

Examples

Below is an exmaple of data encoded in SION.

[
    "array": [
        nil,
        true,
        1,      // Int in decimal
        1.0,    // Double in decimal
        "one",
        [1],
        ["one" : 1.0]
    ],
    "bool": true,
    "data": .Data("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7"),
    "date": .Date(0x0p+0),
    "dictionary": [
        "array" : [],
        "bool" : false,
        "double" : 0.0,
        "int" : 0,
        "nil" : nil,
        "object" : [:],
        "string" : ""
    ],
    "double": 0x1.518f5c28f5c29p+5, // double in hex
    "ext": .Ext("1NTU"),            // 0xd4,0xd4,0xd4
    "int": -42,                     // int in hex
    "nil": nil,
    "string": "漢字、カタカナ、ひらがなの入ったstring😇",
    "url": "https://github.com/dankogai/"
]

As you notice,

• comments are allowed - // up to newline.
• non-String keys are allowed. Any data conforming to SION can be a {Dictionary,Map,Object} key.

And below is an example of JSON-compatible SION…

[
    "array" : [
        nil,
        true,
        1,    // Int in decimal
        1.0,  // Double in decimal
        "one",
        [1],
        ["one" : 1.0]
    ],
    "bool" : true,
    "dictionary" : [
        "array" : [],
        "bool" : false,
        "double" : 0.0,
        "int" : 0,
        "nil" : nil,
        "object" : [:],
        "string" : ""
    ],
    "double" : 42.195,
    "int" : -42,
    "nil" : nil,
    "string" : "漢字、カタカナ、ひらがなの入ったstring😇",
    "url" : "https://github.com/dankogai/"
]

…which turns into a JSON below.

{
    "array" : [
        nil,
        true,
        1,
        1.0,
        "one",
        [1],
        {"one": 1.0}
    ],
    "bool" : true,
    "dictionary": {
        "array": [],
        "bool": false,
        "double": 0.0,
        "int": 0,
        "nil": null,
        "object": {},
        "string": ""
    },
    "double": 42.195,
    "int": -42,
    "nil": nil,
    "string": "漢字、カタカナ、ひらがなの入ったstring😇",
    "url": "https://github.com/dankogai/"
}