There are multiple options and starting points for this activity, such as:
- https://docs.ogc.org/bp/17-084r1/17-084r1.html
- the ISO 19115 UML model
- OGC API Records
- FG-JSON Features
- Plain GeoJSON
Different examples and schemas can be documented here and options testes.
- Start with OGC API Records schema and build an extension, taking and testing elements one by one from one or more starting points
- Try to map the 19115 UML model to a JSON schema (using Shapechange) and test it element by element
- ?