SDMX 3.0: implement "feature 002 Support reference metadata in the Restful APIs" for SDMX-JSON messages about sdmx-json

[dosse]

In order to support the new requirement, it is proposed to:

structure message changes:

• Simplify the model by restricting an MSD to a single report structure – therefore restricting a Metadata Set to report information for a single Report.
• Enhance Information Model for Structure to include Links
  • This mechanism enables zero to many links to be added to any Identifiable structure which can link to Reference Metadata.
  • The links will be in keeping with the linking mechanism in the JSON messages. https://github.com/sdmx-twg/sdmx-json/blob/master/data-message/docs/1-sdmx-json-field-guide.md#linking-mechanism

--> Implemented as translation from xml structure schemas by J

data message changes:

• Give the Metadata Set an Identification (Data Provider Id, Id, Version). This is similar to a Maintainable structure which is maintained by an Agency, the Metadata is maintained by a Data Provider (it could reuse the same inheritance model).
• Enable a Metadata Set to be returned as a Stub, enabling a Data Provider to see what they have provided metadata for, without requiring the full reports to be returned.

"metadataSets": [
{
	"id": "ALB",
	"providerID": "ALB",
	"version": "1.0.0",
}]

[dosse]

Released