$vocabulary : Object<URI, Boolean>
$vocabulary
Object<URI, Boolean>This keyword is used in dialect meta-schemas to identify the required and optional vocabularies available for use in schemas described by that dialect.
| Value | This keyword must be set to an object where each key is a JSON Schema vocabulary URI and each value is a boolean that represents whether the corresponding vocabulary is considered optional (false) or required (true) |
|---|---|
| Kind | Identifier |
| Applies To | Any |
| Base Dialect | 2020-12 |
| Changed In | None |
| Introduced In | 2019-09 |
| Vocabulary | Core |
| Specification | https://json-schema.org/draft/2020-12/json-schema-core.html#section-8.1.2 |
| Metaschema | https://json-schema.org/draft/2020-12/meta/core |
| Official Tests | draft2020-12/vocabulary.json |
| Default | Implementation dependent |
| Annotation | None |
| Affected By | None |
| Affects | None |
| Also See |
The $vocabulary keyword is a mandatory component of a dialect meta-schema
to list the required and optional vocabularies available for use by the schema
instances of such dialect. The vocabularies declared by a dialect meta-schema
are not inherited by meta-schemas that derive from it. Each dialect meta-schema
must explicitly state the vocabularies it imports using the $vocabulary
keyword.
Common Pitfall
Declaring the
$vocabulary keyword in a schema does not
grant that same schema access to such vocabularies. Instead, the $vocabulary
keyword must be set in the dialect meta-schema that describes the desired
schema.
If a vocabulary is marked as required, JSON Schema implementations that do not recognise the given vocabulary must refuse to process schemas described by such dialect. As a notable exception, every dialect must list the Core vocabulary as required, as it is the foundational vocabulary that implements the vocabulary system itself.
Digging Deeper
By convention, every official JSON Schema dialect defines a dynamic anchor called
meta. This serves as an extensibility point for
arbitrary vocabularies to register syntactic constraints that are automatically
applied to every JSON Schema subschema apart from the top-level one.
Examples
The seven required vocabularies declared by the JSON Schema 2020-12 official dialect
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"$id": "https://json-schema.org/draft/2020-12/schema",
"$dynamicAnchor": "meta",
"$vocabulary": {
"https://json-schema.org/draft/2020-12/vocab/core": true,
"https://json-schema.org/draft/2020-12/vocab/applicator": true,
"https://json-schema.org/draft/2020-12/vocab/unevaluated": true,
"https://json-schema.org/draft/2020-12/vocab/validation": true,
"https://json-schema.org/draft/2020-12/vocab/meta-data": true,
"https://json-schema.org/draft/2020-12/vocab/format-annotation": true,
"https://json-schema.org/draft/2020-12/vocab/content": true
},
// ...
}
An example dialect meta-schema that opts-in to the JSON Schema 2020-12 format assertion vocabulary
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"$id": "https://example.com/2020-12-with-format-assertion",
"$dynamicAnchor": "meta",
"$vocabulary": {
"https://json-schema.org/draft/2020-12/vocab/core": true,
"https://json-schema.org/draft/2020-12/vocab/applicator": true,
"https://json-schema.org/draft/2020-12/vocab/unevaluated": true,
"https://json-schema.org/draft/2020-12/vocab/validation": true,
"https://json-schema.org/draft/2020-12/vocab/meta-data": true,
"https://json-schema.org/draft/2020-12/vocab/format-assertion": true,
"https://json-schema.org/draft/2020-12/vocab/content": true
},
"allOf": [
{ "$ref": "https://json-schema.org/draft/2020-12/meta/core" },
{ "$ref": "https://json-schema.org/draft/2020-12/meta/applicator" },
{ "$ref": "https://json-schema.org/draft/2020-12/meta/unevaluated" },
{ "$ref": "https://json-schema.org/draft/2020-12/meta/validation" },
{ "$ref": "https://json-schema.org/draft/2020-12/meta/meta-data" },
{ "$ref": "https://json-schema.org/draft/2020-12/meta/format-assertion" },
{ "$ref": "https://json-schema.org/draft/2020-12/meta/content" }
]
}
An example dialect meta-schema that imports the Core vocabulary as required and the Validation vocabulary as optional
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"$id": "https://example.com/simple-2020-12",
"$dynamicAnchor": "meta",
"$vocabulary": {
"https://json-schema.org/draft/2020-12/vocab/core": true,
"https://json-schema.org/draft/2020-12/vocab/validation": false
},
"allOf": [
{ "$ref": "https://json-schema.org/draft/2020-12/meta/core" },
{ "$ref": "https://json-schema.org/draft/2020-12/meta/validation" }
]
}