@julian example using foaf and sioc...

```
id = f1
type = [as:Service, sioc:Forum]
as:summary = "Forum TF category"

id = g1
type = [as:Group, foaf:Group, foaf:Agent, sioc:User]
as:name = "AP Forum Task Force"
foaf:member = [Julian, a]

id = t1
type = [as:Collection, sioc:Thread]
as:summary = "Some thread"
sioc:has_container = f1

id = p1
type = [as:Event, sioc:Post]
as:name = "Meeting on April 2025"
sioc:has_container = t1
sioc:has_creator = g1
as:attributedTo = g1
```

Nice, but does this mean accounts on NodeBB can no longer mention categories at all?

Perhaps this was not its intended purpose, but being able to link to a category in a post by a handle is much more convenient than typing its entire URL - and that goes for both remote and local categories.

So I am not talking about creating a topic on remote categories by mentioning them, but rather trying to bring attention to their existence to a person that might not know about them.

E.g.
> @test1 Hey, you might want to check out @testing-ground; there's lots of awesome content there.

> @test1 If you want to make a report, consider posting this to @bug-reports instead.

N.B. In my examples, I'm actually still able to mention local categories via a handle - so I did not type [[@testing-ground](https://community.nodebb.org/category/4/testing-ground)](https://community.nodebb.org/category/4/testing-ground), simply [@testing-ground](https://community.nodebb.org/category/4/testing-ground).

@AltCode I think being able to mention categories is handy. It was removed as a byproduct of the category no longer being a user, but it's not gone by design, no. It can come back.

@julian The way cross-posting works on Lemmy and Reddit is basically to copy the post, so there's not necessarily a reason to break the one-to-one mapping of posts-to-categories. (Though, actually, looking at Reddit, I think it's actually a new post with an internal link preview, rather than a wholesale copy of content as it is on Lemmy). But more advanced frameworks could be interesting

@eeeee no problem, what seems straightforward for me isn't always the case for others!

Below the category description, there is a bar that contains buttons for sorting the topic list. The first of those buttons controls whether you are watching or tracking the category. It usually corresponds to whether you see topics from that category in your unread and recent pages.

For remote categories, this controls whether or not you are following the category. If you are following the category, then topics posted in that category will show up in your unread page.

@trwnh@mastodon.social in general, if NodeBB discovers a group, it will create an (initially) empty category in order to house topics.

If in the course of that category's life, no topics actually make it in (i.e. if nobody addresses anything to it, nobody follows it, etc.) then it'll be pruned out as normal.

So if an as:Group contains users, and doesn't share or send creates, then it'll just be a little stub that goes nowhere, that's all.

I would be remiss if I didn't also mention that while this theoretically works with software like PieFed and Mbin, it has only really been tested against NodeBB (of course) and Lemmy.

@andrew_s@piefed.social @rimu@mastodon.nzoss.nz @melroy@kbin.melroy.org

Some interesting bugs atm

All the ActivityPub groups I was following prior to this update were successfully migrated to become remote categories (good!), but now that they are no longer treated as remote users, this has left behind a bunch of "guest" users in my /following page.

Also due to the migration, a bunch of topics that used to be categorised under @activitypub, were automatically moved to [[@activitypub](https://community.nodebb.org/category/30/activitypub)@forum.wedistribute.org](https://community.nodebb.org/category/activitypub@forum.wedistribute.org)!

I presume this happened because [[@activitypub](https://community.nodebb.org/category/30/activitypub)@forum.wedistribute.org](https://community.nodebb.org/category/activitypub@forum.wedistribute.org) is set to mirror @activitypub. I'm guessing that since the group actor was sharing all these posts, once NodeBB recognised it as a remote category instead, it began to treating those share activities as move actions.

Seeing how NodeBB does not have a notion of topics belonging to multiple categories, you might want to revisit how you handle remote categories that follow and mirror local categories.

@AltCode thanks for reporting! I'll take a look at those tomorrow.

The topics being moved out is a byproduct of the migration. Looks like some tweaking is in order! Perhaps I'll only move topics whose main post is on the same domain.

@AltCode I've moved those topics back to the proper category

Edit: updated as had to click into category to follow

@julian@community.nodebb.org

I can confirm it works with Mbin, look at my instance: https://kbin.melroy.org/m/activitypub@community.nodebb.org/p/286459/Happy-Tuesday-Today-we-ve-updated-the-NodeBB-community-forum-onto#post-comment-413326

@julian @activitypub Makes sense. Were NodeBB's own federated categories represented as users prior to this change? Do you assume that all groups are FEP-1b12 groups?
There was an interesting discussion on SocialHub on identifying FEP-1b12 groups and nutomic made a compelling argument that we should just assume that Group supports FEP-1b12 if there is no other indicator:

FEP-1b12: Group federation

Internet forums are probably the oldest form of social media. They can be implemented with the Activitypub protocol, but such implementations may not necessarily be compatible with each other. This document defines a com…

SocialHub (socialhub.activitypub.rocks)

@silverpill@mitra.social good questions!

Local NodeBB categories are still federated out as ActivityPub actors, with as:type Group, they follow 1b12 as they always have.

I do assume that group actors adhere to 1b12, but that doesn't stop others from creating topics by mentioning them directly. If a NodeBB instance happens to hear about that, we'll add it to the remote category.

@AltCode the two bugs you identified have been resolved, can you confirm the latter? The former I manually moved them back already to the right category.

Confirmed working with:

• PieFed Communities: PieFed Meta
• Flipboard Magazines: [Gear by @engadget@flipboard.com](https://community.nodebb.org/category/gear-engadget@flipboard.com)

However, while Flipboard magazines send Announces as per 1b12, and the items are added to the outbox, the objects themselves do not address the magazine at all, and so a backreference is missing. When they come into NodeBB, there's no pointer back to the group, and so it is slotted into the "uncategorized" bucket.

cc @mike@flipboard.social

tl;dr — can this object https://flipboard.com/users/Engadget/statuses/uva9misBSrqjCSR6mtzV6g:a:3199686 please include https://flipboard.com/@engadget/gear-nv6v86arz in its to or cc property?