Not working with the GEOBON STAC catalogue

[tpoisot]

The following is empty:

using STAC
catalog = STAC.Catalog("https://stac.geobon.org/")
entry = catalog["chelsa-clim"]

Specifically, the output is

julia> entry = catalog["chelsa-clim"]
chelsa-clim
CHELSA Climatologies
CHELSA Climatologies
License: CC-BY-SA-4.0

But using the URL gives a list of the expected items withing this collection: https://stac.geobon.org/collections/chelsa-clim/items

Is there something I am missing?

[Alexander-Barth]

Thanks for the reproducer. The code is looking for item (without the endings s):

https://github.com/JuliaClimate/STAC.jl/blob/e163edb7728c8e62c20c461fe775ab25f6302e63/src/catalog.jl#L118

In stac.geobon.org's JSON however, the rel field has the value items (with an s):

julia> entry = catalog["chelsa-clim"];

julia> entry.data.links
4-element JSON3.Array{JSON3.Object, Base.CodeUnits{UInt8, String}, SubArray{UInt64, 1, Vector{UInt64}, Tuple{UnitRange{Int64}}, true}}:
 {
    "rel": "items",
   "type": "application/geo+json",
   "href": "https://stac.geobon.org/collections/chelsa-clim/items"
}
 {
    "rel": "parent",
   "type": "application/json",
   "href": "https://stac.geobon.org/"
}
 {
    "rel": "root",
   "type": "application/json",
   "href": "https://stac.geobon.org/"
}
 {
    "rel": "self",
   "type": "application/json",
   "href": "https://stac.geobon.org/collections/chelsa-clim"
}

See the spec: https://github.com/radiantearth/stac-spec/blob/2e6947df194a707354d6d5be1da6762647ee593f/commons/links.md#link-object

and example:

https://github.com/radiantearth/stac-spec/blob/2e6947df194a707354d6d5be1da6762647ee593f/examples/collection.json#L93

Does the spec also mentions items in plural for the rel field?

[tpoisot]

Thanks @Alexander-Barth -- you are right, neither the spec nor the types for link relations in IANA use items

@jmlord / @glaroc -- it seems that the GEOBON STAC catalogue isn't following the spec

[glaroc]

We are using STAC Fastapi. This might be a difference between STAC spec and STAC API spec ? Other catalogs I'm looking at use items with an "s".

https://planetarycomputer.microsoft.com/api/stac/v1/collections/terraclimate https://eocat.esa.int/eo-catalogue/collections

[tpoisot]

Yeah, the STAC API spec is different from the STAC spec 😕

[Alexander-Barth]

That would be a real bummer. The STAC spec is already quite extensive as is. Or maybe it is an extension (https://stac-extensions.github.io/) or a beta version of the spec (just a speculation). Maybe the raising an issue at https://github.com/radiantearth/stac-spec/ would help?

[glaroc]

In any case, if catalogs like the Planetary Computer and ESA have items instead of item, this library should probably support it. Otherwise, many users will face similar issues. The rstac R package and the Python pystac library work fine with our catalog.

[Alexander-Barth]

Are you able to read the items with pystac? This is what I tried, but I got also an empty list for the items.

import pystac
root_catalog = pystac.Catalog.from_file("https://stac.geobon.org/")

root_catalog.get_child("chelsa-clim").title
# output 'CHELSA Climatologies'

list(root_catalog.get_child("chelsa-clim").get_items())
# output []

list(root_catalog.get_child("chelsa-clim").get_items(recursive=True))
# output []

pystac.__version__
# output '1.10.1'

I am not very familiar with pystac, I followed the documentation here https://pystac.readthedocs.io/en/stable/quickstart.html#Crawling-Items

[glaroc]

@Alexander-Barth I believe you have to use pystac_client: https://pystac-client.readthedocs.io/en/latest/usage.html

Static and dynamic catalogs have different characteristics. For example, sub-catalogs are not allowed with the STAC API Spec, while they are in the STAC Spec. I guess items vs item is another difference.

[Alexander-Barth]

This seems to be relevant:

https://github.com/radiantearth/stac-api-spec/blob/604ade6158de15b8ab068320ca41e25e2bf0e116/overview.md?plain=1#L40