Does eoAPI support nested collections?

[zbenta]

I was trying to create some nested collections as follows.

Parent:

{
  "id": "PARENT",
  "type": "Collection",
  "stac_version": "1.0.0",
  "title": "Sentinel PARENT Collection",
  "description": "This is the parent collection containing Sentinel-2 sub-collections.",
  "license": "proprietary",
  "keywords": ["Sentinel-2", "Earth Observation", "Satellite Data"],
  "providers": [
    {
      "url": "https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi",
      "name": "European Union/ESA/Copernicus",
      "roles": ["producer", "licensor"]
    }
  ],
  "extent": {
    "spatial": {
      "bbox": [[-9.84375, 36.5626, -5.866699, 42.334184]]
    },
    "temporal": {
      "interval": [["2015-01-01T00:00:00Z", null]]
    }
  },
  "links": [
    {
      "rel": "root",
      "type": "application/json",
      "href": "http://localhost:8081/"
    },
    {
      "rel": "self",
      "type": "application/json",
      "href": "http://localhost:8081/collections/PARENT"
    },
    {
      "rel": "child",
      "type": "application/json",
      "href": "http://localhost:8081/collections/CHILD1",
      "title": "Sentinel CHILD1 Collection"
    }
  ]
}

Child:

{
  "id": "CHILD1",
  "type": "Collection",
  "stac_version": "1.0.0",
  "title": "Sentinel CHILD1 Level 1C/2A Sentinel-2 images",
  "description": "The Copernicus Sentinel-2 mission consists of two polar-orbiting satellites that are positioned in the same sun-synchronous orbit, with a phase difference of 180°. It aims to monitor changes in land surface conditions. The satellites have a wide swath width (290 km) and a high revisit time. Sentinel-2 is equipped with an optical instrument payload that samples 13 spectral bands: four bands at 10 m, six bands at 20 m and three bands at 60 m spatial resolution.",
  "license": "proprietary",
  "keywords": ["Sentinel-2", "experimental"],
  "providers": [
    {
      "url": "https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi",
      "name": "European Union/ESA/Copernicus",
      "roles": ["producer", "licensor"]
    }
  ],
  "extent": {
    "spatial": {
      "bbox": [[-9.84375, 36.5626, -5.866699, 42.334184]]
    },
    "temporal": {
      "interval": [["2015-01-01T00:00:00Z", "2015-12-31T23:59:59Z"]]
    }
  },
  "links": [
    {
      "rel": "root",
      "type": "application/json",
      "href": "http://localhost:8081/"
    },
    {
      "rel": "self",
      "type": "application/json",
      "href": "http://localhost:8081/collections/CHILD1"
    },
    {
      "rel": "parent",
      "type": "application/json",
      "href": "http://localhost:8081/collections/PARENT",
      "title": "Sentinel PARENT Collection"
    },
    {
      "rel": "items",
      "type": "application/geo+json",
      "href": "http://localhost:8081/collections/CHILD1/items"
    }
  ]
}

I create both of them by posting the specifif json into the /collections endpoint.
When I query the collection endpoint I don't see any hierarchycal structure between the "PARENT" and "CHILD":

Also, when I inspect the "CHILD1" collection the parent is always the root collection and not "PARENT"

{
  "id": "CHILD1",
  "type": "Collection",
  "links": [
    {
      "rel": "items",
      "type": "application/geo+json",
      "href": "http://localhost:8081/collections/CHILD1/items"
    },
    {
      "rel": "parent",
      "type": "application/json",
      "href": "http://localhost:8081/"
    },
    {
      "rel": "root",
      "type": "application/json",
      "href": "http://localhost:8081/"
    },
    {
      "rel": "self",
      "type": "application/json",
      "href": "http://localhost:8081/collections/CHILD1"
    },
    {
      "rel": "items",
      "href": "http://localhost:8081/collections/CHILD1/items",
      "type": "application/geo+json"
    },
    {
      "rel": "http://www.opengis.net/def/rel/ogc/1.0/queryables",
      "type": "application/schema+json",
      "title": "Queryables",
      "href": "http://localhost:8081/collections/CHILD1/queryables"
    }
  ],
  "title": "Sentinel CHILD1 Level 1C/2A Sentinel-2 images",
  "extent": {
    "spatial": {
      "bbox": [
        [
          -9.84375,
          36.5626,
          -5.866699,
          42.334184
        ]
      ]
    },
    "temporal": {
      "interval": [
        [
          "2015-01-01T00:00:00Z",
          "2015-12-31T23:59:59Z"
        ]
      ]
    }
  },
  "license": "proprietary",
  "keywords": [
    "Sentinel-2",
    "experimental"
  ],
  "providers": [
    {
      "url": "https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi",
      "name": "European Union/ESA/Copernicus",
      "roles": [
        "producer",
        "licensor"
      ]
    }
  ],
  "description": "The Copernicus Sentinel-2 mission consists of two polar-orbiting satellites that are positioned in the same sun-synchronous orbit, with a phase difference of 180°. It aims to monitor changes in land surface conditions. The satellites have a wide swath width (290 km) and a high revisit time. Sentinel-2 is equipped with an optical instrument payload that samples 13 spectral bands: four bands at 10 m, six bands at 20 m and three bands at 60 m spatial resolution.",
  "stac_version": "1.0.0"
}	

Any ideas on how to create nested collection? Since nested catalogs, from what I know, are not possible, I have no idea how to solve this.

[hrodmn]

Hi @zbenta - this would involve changes to pgstac and as of now there are no plans to support hierarchically organized collections but you can follow along with this issue stac-utils/pgstac#88

[zbenta]

Thanks for the update @hrodmn, I was wondering why on earth "CHILD" had the root collection as parent when I specifically told it that "PARENT" was his actual parent.
By the way, when looking into the database we can clearly see the parent definition.

And also while using the stac-browser, we can see the children of the parent collection.

Still, this would be a great addition to the project, I'll subscribe to issue 88 to get notified if someone implements it.

[bitner]

That is actually probably coming from stac-fastapi-pgstac. PGStac does not modify any of the links at all, but stac-fastapi adjusts the links to make sure that all the links are relative to the url that the service is deployed on.

See https://github.com/stac-utils/stac-fastapi-pgstac/blob/main/stac_fastapi/pgstac/models/links.py