$vocabulary uri vs meta-schema $id

[redmitry]

Hello,

I'd like to implement meta-schema (2019-09 $vocabulary) support in my json schema validator and have trouble to figure out the relationship between $vocabulary uri and actual meta-schema (with some $id) to validate.

If I understand correctly the spec. $vocabulary completely defines which vocabularies (meta-schemas) must be used for the validation.
What I do not understand is the link between them.

For instance:
https://json-schema.org/draft/2019-09/json-schema-validation.html#rfc.section.6
says that
https://json-schema.org/draft/2019-09/vocab/validation
matches
https://json-schema.org/draft/2019-09/meta/validation

So I can hardcode that in the validator (as well as all "core", "applicator", "format", etc...), But how I would match custom meta-schemas?

If the $vocabulary uris had meta-schemas $id, in a case of for instance

"https://json-schema.org/draft/2019-09/ meta /format": false
I would just substitute "https://json-schema.org/draft/2019-09/meta/format" schema with "true" (always valid).

Does $vocabulary has any effect to the validator or it is only metadata and actual validation is performed over (meta) schema?

{
    "$schema": "https://json-schema.org/draft/2019-09/schema",
    "$id": "https://json-schema.org/draft/2019-09/schema",
    "$vocabulary": {
        "https://json-schema.org/draft/2019-09/vocab/core": true,
        "https://json-schema.org/draft/2019-09/vocab/applicator": true,
        "https://json-schema.org/draft/2019-09/vocab/validation": true,
        "https://json-schema.org/draft/2019-09/vocab/meta-data": true,
        "https://json-schema.org/draft/2019-09/vocab/format": false,
        "https://json-schema.org/draft/2019-09/vocab/content": true
    },
    "$recursiveAnchor": true,

    "title": "Core and Validation specifications meta-schema",
    "allOf": [
        {"$ref": "meta/core"},
        {"$ref": "meta/applicator"},
        {"$ref": "meta/validation"},
        {"$ref": "meta/meta-data"},
        {"$ref": "meta/format"},
        {"$ref": "meta/content"}
    ],

What consequence ".../format": false has here?

Any help is highly appreciated :-)

D.

[Julian]

This probably belongs more on the community repo (as it has to do with understanding the spec more so than the test suite) -- you may also want to join the #implementers channel on the JSON Schema slack to ask it.

But the short answer is that : false there means "the format vocabulary is optional when evaluating instances against this dialect", so your implementation should proceed even if it doesn't know anything about the format keyword.

To be abundantly clear as well,

If I understand correctly the spec. $vocabulary completely defines which vocabularies (meta-schemas)

Vocabularies are not the same as meta-schemas, vocabularies are:

tightly related collection of keywords, grouped to facilitate re-use

and they may come along with zero or more meta-schemas which validate the keywords inside of themselves, but the URL you see is otherwise just an identifier for some vocabulary.

Do feel free to follow up if you have further questions, though as I say perhaps we should transfer this discussion elsewhere.

[redmitry]

Hi Julian,

Thank you for pointing to the Slack - a lot of info there.
I think I understand it now... better.

Kind regards,

Dmitry