Context deletion vs. Removal brainstorming

[julian@activitypub.space]

Currently I am grappling with the specifics behind how to federate out the deletion of a topic in a category (or in ForumWG terms, the deletion of a context from an audience.)

For those unaware, a context is essentially an OrderedCollection containing all objects within its purview.

Deleting a note or other object is easy. If you are same-origin as the object, you Delete(Object), done.

Deleting a context is more difficult... you can't rely on other implementors to store references to your contexts, since it is essentially meaningless to them. Furthermore, if a context is deleted, then when a Delete(Context) is federated out, receivers will have no idea what they're seeing, will try to retrieve the object, and find a 404. So it doesn't even work at all.

Even worse, you can't really delete other peoples' contexts (or for that matter, their content) since you're not same-origin.

Finally, I realized I'm looking at this the wrong way — I'm not deleting contexts, I'm simply removing them from an audience. Remove works perfectly fine when the context continues to exist (as it can be referenced and duck typed). Remove also works for remote content; the same-origin check applies to the audience you're removing from.

If you're deleting a context, you have to be the same-origin, and you really should just federate out deletion of the local members in that collection, via regular Delete(Object).

I suppose federating out self-destruction of a context would be the most complete but it is quite difficult to do when it is no longer resolvable...

[silverpill@mitra.social]

@julian I forgot, why do you want to delete a context? If it's your thread, isn't it enough to just Delete the top-level post?

[julian@activitypub.space]

I'm looking into federating out deletion of contexts because in NodeBB the concept of a topic is a discrete entity, not tied to the posts contained within. Deleting the top-level post would not alter the topic in any way, except perhaps that the next oldest reply is suddenly promoted to top-level, which is odd.

Conversely, in ActivityPub, there either is no concept of a context (threaded objects only), or merely the suggestion of one as a view (current implementations of resolvable contexts). I'm hoping to move this more towards contexts as discrete entities with their own activities.

[silverpill@mitra.social]

I think context property should point to a collection (a dynamic view), but we can introduce a new Delete-able object that is linked to that collection. It could be an actor: https://codeberg.org/fediverse/fep/src/branch/main/fep/f06f/fep-f06f.md

You also mentioned Remove, how it should look in practice? Remove from what target?

[julian@activitypub.space]

At least from the point of view of NodeBB, when a topic is deleted, the Collection is de facto gone. That's why it's problematic to federate out a delete because nobody else can resolve it to find their "version" of your context.