Review of more recent versions of JSON Schema

[jpmckinney]

Discussion

The Draft-04 we're using matches draft-zyp-json-schema-04 / draft-fge-json-schema-validation-00.

http://json-schema.org/draft-06/json-schema-release-notes.html matches draft-wright-json-schema-00, draft-wright-json-schema-01 / draft-wright-json-schema-validation-00, draft-wright-json-schema-validation-01

• Draft-06 is tidier and adds validation properties, but nothing is added that allows OCDS to express more of its normative rules in schema
• Since we're already maintaining a separate metaschema, we can implement examples in the schema, if we wanted to. (It would just be ignored in Draft 04.)

http://json-schema.org/draft-07/json-schema-release-notes.html matches draft-handrews-json-schema-00, draft-handrews-json-schema-01 / draft-handrews-json-schema-validation-00, draft-handrews-json-schema-validation-01

• Adds "if", "then", "else" validation, which is quite powerful, allowing conditionally required fields, for example
• Adds a date format, which we don't presently need, but which could be a good addition
• Adds "$comment", if we want to include notes for schema maintainers in the schema itself

http://json-schema.org/draft/2019-09/release-notes.html matches draft-handrews-json-schema-02

• Adds a duration format, which could serve to replace durationInDays
• Adds a deprecated boolean keyword, which we had implemented ourselves as an object

Changelogs

• http://json-schema.org/draft/2019-09/json-schema-core.html#rfc.appendix.G
• http://json-schema.org/draft/2019-09/json-schema-validation.html#rfc.appendix.C

Proposal

No action. This issue just serves to document relevant changes to JSON Schema. Any further work should consider the effort to update OCDS validators, especially with respect to maintaining clarity in error messages.

[jpmckinney]

To upgrade between draft versions, see https://github.com/ajv-validator/json-schema-migrate

Edit: BODS experience of upgrading: https://github.com/openownership/data-standard/issues/469 https://github.com/openownership/data-standard/pull/485