How to recognize what has been updated in a catalog

[chiarch84]

Dear all, is there a way to expose in a STAC Catalog only the updated Collections and Items in a specific time range?
Something similar to OAI-PMH standard?

I have this issue on provider side, but also in retrieving data from existing STAC catalogs. How do I know that the data in the catalog changed? And how do I only get what has been updated? I ask it since for big catalogs it is not possible to just redownload everything every time.
Thanks.

[m-mohr]

Collection and Item Search with CQL based on the updated or created field, I guess? It's a bit cumbersome though so maybe something for a STAC API extension.

[antoine-de]

I have the same need, I need a way to find what has changed since a specific date (for my use case, since the last crawl of the API).

I was planning to implement something like CQL on collections (enough for my usecase (https://api.panoramax.xyz/) I think), but our data can also be deleted by the users, I don't really know how to fit this in the model.
I can always add a specific route to get the deleted collections since a date, but now sure if it's the right way to approach this.