Should JSON-schema require documents to declare `$schema` (be self-referential)? - json

Question

JSON-schema says that a JSON document can declare the schema to which the document conforms using the $schema property. Example:
{
"$schema": "http://example.com/example_fancy_schema#",
"example_fancy_property": "cute fluffy kittens"
}
where the schema looks like:
{
"$schema": "http://json-schema.org/draft-04/schema#",
"title": "Example Fancy Schema",
"description": "The schema that describes the example format.",
"type": "object",
"properties": {
"example_fancy_property": {
"type": "string",
"enum": ["cute fluffy kittens"]
}
},
"additionalProperties": false,
"required": [ "example_fancy_property" ]
}
Does this mean that one should add a property for this in the actual schema, e.g.:
{
"$schema": "http://json-schema.org/draft-04/schema#",
"title": "Example Fancy Schema",
"description": "The schema that describes the example format.",
"type": "object",
"properties": {
"$schema": {
"type": "string",
"enum": ["http://example.com/example_fancy_schema#"]
},
"example_fancy_property": {
"type": "string",
"enum": ["cute fluffy kittens"]
}
},
"additionalProperties": false,
"required": [ "$schema", "example_fancy_property" ]
}
None of the examples on the JSON-schema website appear to declare this, so I suspect one isn't supposed to declare it. But I'm curious anyway :)

Answer 1

The $schema keyword is recommended for use in JSON Schemas, to denote the version of the schema standard being used.
However, it has no special meaning in data. Over HTTP, there are recommended ways to associate data with a schema, but the $schema property is not one of them.