Collection and Catalog inheritance

[matthewhanson]

We recently talked about changing the spec so that Collection does not inherit from Catalog, but I'm having trouble finding where there was wording changes to reflect that. There also doesn't appear to be anything in the CHANGELOG about it.

@pgadomski pointed out where the spec still allows a root link to point to a Collection. But since a Collection is no longer a Catalog, it cannot serve as a root catalog.

[gadomski]

I found two other references to collections-as-root.

[m-mohr]

That Collections can't be a root seems also be to be an issue, but more for the API, right? Why should we restrict that?

[matthewhanson]

@m-mohr not sure what you mean, in an API you'd always have a root catalog.
For static catalogs if we want Collections to act as a root then we'd have to change the spec to specify that a Catalog or a Collection can be a root object

[m-mohr]

That's what I meant to express. Root catalogs should be allowed to be Collections. It is allowed since 0.6, why drop this now? I don't see a good reason. (Dropping inheritance for the type field is not a good reason IMHO.)

But since a Collection is no longer a Catalog, it cannot serve as a root catalog.

Why? Is this just because the name is "root catalog" and not "root catalog or collection"?

It feels like the addition of type and removal of inheritance is giving us more issues than it solves problems...
This is a good example of why we should avoid last-minute breaking changes, I think.

[matthewhanson]

Correct a root Catalog is a "Catalog", not a Collection. If we want to define that a Root can be Catalog or Collection that's fine, but as it stands I don't think a Collection can act as a root Catalog because it's not a Catalog.

[cholmes]

+1 to define a root catalog to also be a collection. Intent of the change to me was to have everything operate as it has before. So we should change the definition to say the root can be a catalog or a collection.

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On Thu, Apr 8, 2021, 3:09 AM Matthias Mohr ***@***.***> wrote: That's what I meant to express. Root catalogs should be allowed to be Collections. It is allowed since 0.6, why drop this now? I don't see a good reason. (Dropping inheritance for the type field is not a good reason IMHO.) — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1082 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AADDL2MYFCV2DQF6WI6MXXTTHV6HNANCNFSM42NOVNXQ> .

[matthewhanson]

Does it make sense to word this as saying that a Collection can act like a Catalog? Or do we explicitly state that a root object can be a Catalog or Collection?

[cholmes]

I think we should say both. I do think we should be explicit that a root object can be caalog or collection.

[jisantuc]

@matthewhanson can you say more about "a root Catalog is a "Catalog", not a Collection" ? Where is that specified? I think this has more to do with slippage about catalogs vs. Catalogs than it does to do with the type and broken inheritance.

[matthewhanson]

@jisantuc I think you are probably right, a root Catalog has been referred to as a capital-C Catalog, implying that it is a STAC Catalog. Maybe it's just a root catalog, where catalog can be Catalog or Collection. Which is fine, if not a tad confusing

[cholmes]

Just looked through the occurrences for root and there's definitely room to improve a number of them. I can take on going through and improving, will make a PR

[m-mohr]

Finds most occurances: /(root|parent)\s+(STAC\s+)?catalog/i ;-)