- A catalog of catalogs is not possible within the STAC API. The entry level is the only catalog. A catalog shall only contain collections.
- A collection can contain *child*s of different types. This child can be a collection.
- A collection of collections is
- useful to show a landing page for upper level hierarchy elements like *institution* which can display everything this element is connected to
- does not improve search functionality. Afaik, the stac browser's search does not go through a nest of collection.
## Which collections should have items?
To avoid duplication of items in the data base, it is key to define a lowest collection level at which items (whatever items will be) are added to a collection. In Warmworld, *"experiment"* is the collection level which contains items.
From a CMIP perspective, that means that DRS elements that follow deeper in the hierarchy, like `realm` or `variable_id`, would not be represented in the STAC hierarchy of catalog,collection and item but rather become a queryable. Users would need to search for variables and realizations instead of getting it through browsing only.
## What names should assets have?
The data base cannot handle differently named assets within a collection. Therefore, an asset should not be named like a file since this is usually unique. The file name can be an attribute of the asset while the asset will have a name like `data0001`. See the CEDA API for an example.
## How to add queryables?
Needs to be added at two points in the source code:
