JSOG - JavaScript Object Graph

JSOG (JavaScript Object Graph) is a simple convention which allows arbitrary object graphs to be represented in JSON. It allows a large, complicated, cyclic object graph to be seriazlied and deserialized to and from JSON.

The problem with JSON

JSON is widely used as a data interchange format, however, it is limited:

• Only directed acyclic graphs can be represented.
• Graphs with repeating information are duplicated on the wire and in memory.

For example:

[
	{
		"name": "Sally",
		"secretSanta": {...Bob...}
	},
	{
		"name": "Bob",
		"secretSanta": {...Fred...}
	},
	{
		"name": "Fred",
		"secretSanta": {...Sally...}
	}
]

This graph has cycles. Your database can represent these relationships just fine and your ORM can pull the object graph (with references) into memory, but you cannot directly serialize to a JSON structure without stack overflow errors.

The JSOG solution

JSOG is a standard way to represent object graphs.

• JSOG is 100% JSON. No special parser is necessary.
• JSOG is human readable; graphs without cycles look like regular JSON.
• JSOG does not require (or interact with) pre-existing id fields.
• JSOG is fully self-describing; ids and refs are unambiguous.
• JSOG is easy to implement in any language or platform.

This is the JSOG representation of the aforementioned graph:

[
	{
		"@id": "1",
		"name": "Sally",
		"secretSanta": {
			"@id": "2",
			"name": "Bob",
			"secretSanta": {
				"@id": "3",
				"name": "Fred",
				"secretSanta": { "@ref": "1" }
			}
		}
	},
	{ "@ref": "2" },
	{ "@ref": "3" }
]

• @id values are arbitrary strings.
• @id definitions must come before @ref references.

Serializing to JSOG

Each time a new object is encountered, give it a unique string @id. Each time a repeated object is encountered, serialize as a @ref to the existing @id.

Deserializing from JSOG

Track the @id of every object deserialized. When a @ref is encountered, replace it with the object referenced.

Implementation

JSOG is designed to be easily implemented across platforms. Look at the existing implementations; most are a couple dozen lines of code.

JavaScript

The github project which contains this README includes a JavaScript implementation of JSOG. It can be used to convert between a cyclic object graph and JSOG strings:

string = JSOG.stringify(cyclicGraph);
cyclicGraph = JSOG.parse(string);

Or it can be used to convert between object graphs directly:

jsogStructure = JSOG.encode(cyclicGraph);	// has { '@ref': 'ID' } links instead of cycles
cyclicGraph = JSOG.decode(jsogStructure);

Other Languages

• Java: a Jackson plugin
• Python: a Python implementation
• Ruby: a Ruby implementation

Please contact us about other implementations so they can be linked here.

Authors

The authors are:

• Jeff Schnitzer (jeff@infohazard.org)
• Jon Stevens (latchkey@gmail.com)

License

This specification and software are provided under the MIT license