CswCatalogGroup: add support for nested Terria catalogues (like TerriaReference)

[pvgenuchten]

I have a scenario where users want to describe terria maps in a catalogue. Current challenges

• the csw-catalogue-group filters all records which do not link to a wms, it should include records which link to a terria map
• the data link is some form of a map definition, for example http://foo.com/?start={share-map-definition}, or foo.com/#mymap (suggestions?). Would be interesting to load those layers on top of the existing map? Or better to load in a new window?

is this a useful usage scenario for people?

[nf-s]

This is a interesting use-case of CSW - I don't believe I have come across it before. I think there would be challenges with applying startData when a user clicks on a record like this. But, I think it would be relatively easy to have a CSW record with a data link to a Terria Catalog JSON file that gets loaded as a "sub-catalog" - we already have a function called TerriaReference.

For example

{
  "catalog": [
    {
      "name": "agriculture",
      "url": "https://terria-catalogs-public.storage.googleapis.com/nationalmap/catalog/agriculture/prod.json",
      "id": "agriculture",
      "type": "terria-reference",
      "isGroup": true
    }
  ]
}

• Open this link
• Open catalog and click on "Some external catalog"
• This will load an external catalog (here)

This can also be used to load single items - for example

{
  "catalog": [
    {
      "name": "Forests of Australia",
      "path": [
        "cEynH3ca",
        "SjtbqJgr"
      ],
      "type": "terria-reference",
      "url": "https://terria-catalogs-public.storage.googleapis.com/nationalmap/catalog/agriculture/prod.json"
    }
  ]
}

• Open this link
• here the path property is an array of nested groups inside the external catalog
  • "cEynH3ca", "SjtbqJgr" maps to
  • "Agriculture" -> "Forests of Australia (2018)"

We would need to add some way of matching a CSW Record URI protocol or scheme as a TerriaReference - and maybe somehow add some support for the path property

[pvgenuchten]

A potential service type/protocol would be ‘terria-map-config’,interesting to register it then at
https://github.com/OSGeo/Cat-Interop

ogc also has a standard called ows-context which is a subset of a terria map config, but still interesting for interoperability. Ows context already has a assigned service type in cat interop