Yes, in which case they're not strictly federated with them. If you click "All" in that instance, no posts from the missing instance will show up. The "All" list shows all instances that the instance is federated with.

They're not explicitly defederated, necessarily, but they're not federated, not until a user subscribes.

I'm not sure how it works in either direction. Like, if a user from one instance subscribes to another, but no users from the other instance subscribes to the first, then the federation will maybe only be one way.

[–] Barbarian@sh.itjust.works 3 points 1 year ago (1 children)

This isn't quantum physics, where an instance exists in a superposition of federated and defederated.

Just because an instance is federated, doesn't mean they're linked. Federated means data can by synced across. Linked means that data is being synced across. What is synced depends on what people are subscribed to.

[–] TWeaK@lemm.ee 3 points 1 year ago* (last edited 1 year ago) (1 children)

That's very pedantic of you, but fair enough, more or less.

Looking it up, they're all considered types of federation. The instances page shows the instances in the Allowlist. Other instances that aren't in the Blocklist (defederated) are in Open federation. Even the Blocklist is considered a type of federation, per the lemmy docs.

Federated just means that it's possible that data could be synced across, ie they're on the same network. Not that it necessarily can be synced across, due to defederation/Blocklist.

[–] Barbarian@sh.itjust.works 2 points 1 year ago

Yeah, I am normally a bit pedantic, sorry about that :)

Yup! That's exactly right. The only slight correction I can offer is that an instance can have either a blocklist or allowlist, it can't have both. If an allowlist exists, then anything not on it is implicitly blocked. If it does not, then anything not in the blocklist is allowed. If it has neither, it's in open federation (everything is allowed).