UAD extent

[cmheazel]

Should we add support for the Uniform Additional Extent to the collection information? Is it mandatory or a separate requirements class?

[jerstlouis]

It's mandatory for Coverages, but it is only applicable for collections supporting dimensions beyond space & time.

[cmheazel]

10/20/21 - if you are an API-Coverage and you support more than space and time dimensions then you shall implement the UAD extent. We will define UAD Extent in API-Common Part 3

[cmheazel]

UAD Extent is currently required for all API-Collections implementations. This would not be a problem if the schema is a proper extension to the Extent schema defined in Common. This needs to be verified.

[jerstlouis]

@cmheazel It might be quite difficult (impossible?) to write an OpenAPI definition that imposes the additional restrictions only for some {collectionId}s. This is part of my argument as why I would have liked those restrictions to be built-in in the first place.

However, it should not pose a problem from the specification's perspective. The additional requirements / API module are only referenced for specifications that wish to include those additional requirements.

Somewhat related to:

https://github.com/opengeospatial/ogcapi-common/issues/302

• OpenAPI's lack of templated path parameters – cannot enumerate based on context
  • Templated ref as a solution: $templatedRef: ../../api/styles/{collectionId}
  • https://github.com/OAI/OpenAPI-Specification/issues/1693
  • https://github.com/OAI/OpenAPI-Specification/issues/2453
  • https://github.com/json-schema-org/json-schema-vocabularies/issues/35
  • https://github.com/json-schema-org/json-schema-vocabularies/issues/36

[jerstlouis]

Coverages now has a requirement on UAD extent, including the grid property allowing to describe regular and irregular grids, and the requirements allowing to describe sparse intervals as additional following the first "overall" lower and upper bound of a dimension (exactly as with "temporal"). The UAD requirements would automatically apply to collections with an [ogc-rel:coverage] link.

I suggest that we also define a requirement class in Common - Part 2 which would specify that it applies to all collections of the API. cc. @joanma747