Remove SELF_CONTAINED as a Catalog type

[matthewhanson]

catalog_type distinguishes between ABSOLUTE_PUBLISHED, RELATIVE_PUBLISHED, and SELF_CONTAINED.

However the only different between RELATIVE_PUBLISHED and SELF_CONTAINED is that there is no self link on the root catalog of a SELF_CONTAINED catalog.

I don't think this is enough of a difference to warrant calling out as a catalog type. For one, the absolute self link at root isn't really used in most (all?) tooling other than for user to know where the root cat lives. I guess stac-browser uses it to display and create the absolute link for it.

You can always just ignore the self link or remove it entirely. Or we could just have an option to save it or now when you save a catalog (include_self_on_root). This is clearer than having a catalog type where it isn't obvious what the practical difference is.

[lossyrob]

I'd want to see this change in the spec before implementing in PySTAC, so if we were to go this route it would be after 1.0. Perhaps move this to a stac-spec issue?

[gadomski]

I find SELF_CONTAINED very useful, e.g. when creating example catalogs for stactools-packages: https://github.com/stactools-packages/usda-cdl/blob/688e7f3defe0e2f8dfdb235eb019d07cf2bebe88/scripts/create_examples.py. So I'm 👎🏽 on this change. @matthewhanson this is a pretty old ticket -- do you still agree with your past self?

[matthewhanson]

Yeah, I sorta do still agree with myself, but not super strongly. It just seems like a the wrong place to make such distinction. The spec isn't really clear that these are all different types of Catalogs (first, it's not clear what "Catalog Type" is since it's not defined), and not intuitive that a self contained catalog just means there's no self link at the root.

Seems like an option for including or excluding self should be an explicit option rather than defined by some vague type (overloaded term) which doesn't do anything beyond that.

All that being said, some things you have to learn to live with and it's been a while so if people find it useful then so be it.

[gadomski]

I agree with your general sentiment about catalog types, but what pystac has (mostly) aligns with the best practices: https://github.com/radiantearth/stac-spec/blob/master/best-practices.md#self-contained-catalogs. IMO any changes should be made to the best practices document first, then trickle down to pystac?