If that object is the root-level node, and it is deleted, everything below it is also deleted.

This is not exactly true. When Lemmy receives Delete/Object for a (top level) post, it only marks the post itself as deleted. The replies are not marked as deleted in the database, but are (currently) hidden in the UI. For 1.0 this behaviour is already changed in the API and UI so that deleted posts are removed from listings, but accessible by direct link so that comments can be viewed. This doesnt involve any change to federation and is an implementation detail.

Adding a new activity type for each such implementation detail is not feasible, and we cannot support all of them. So to maximize compatibility you should definitely keep using Delete(Object), and add a new property if you need to be explicit about it.

This is slightly different from OP as you are talking about deleting a reply (ie Note) with children, while OP is about deleting a top-level post with children. Nevertheless both can be represented in the same way over federation.

Just sending out an individual Delete for every Object. I like this option the least, but it is very easy to implement and needs no changes in other software to work.

This would be terrible for performance when removing dozens or hundreds of comments at once. Rule of thumb should be one activity for one user action.

Make the target of the Delete an array. I’m honestly 50/50 on whether this is actually spec compliant, it’s not clear to me that it isn’t;

The problem with this is that some platforms might get the idea to delete multiple unrelated comments with a single activity, or even comments in different posts. Handling that would make the receiving logic unnecessarily complicated, and would also make it complicated to combine the modlog entries.

Same as option 1, a new property like removeChildren;

This is the simplest and best option.

@nutomic > Make the target of the Delete an array

It technically is because of JSON-LD (everything can be an array), however, software may not support it because it's pretty common for devs to treat AP as JSON instead of JSON-LD, so doing an assessment of compatibility would be suggested

@tofeo  :verified: @julian ...where "always" means "since before there was even Mastodon".

A side-effect of their model, present at least on Hubzilla and Hubzilla's descendants, including still existing (streams) and Forte, is that comments/replies cannot exist in a stream without a) a parent and b) a start post. On all of them, including Friendica, it isn't a post if it replies to something, very much unlike Mastodon where a thread is a bunch of posts.

Depending on whom you ask, a conversation looks either like this:

• Post
  
  • Comment
    
    • Comment
      
      • Comment
  • Comment
    
    • Comment
      
      • Comment

or like this:

• Post
  
  • Comment
    
    • Reply
      
      • Reply
  • Comment
    
    • Reply
      
      • Reply

And by default, you always see it like this, very much unlike Mastodon where you only see single-message piecemeal in any timeline, and you have to dig deep to see a whole thread.

If you delete a comment or a reply, this won't just remove the comment from the conversation and rip a hole into the branch in the conversation where the comment used to be. Instead, it will delete the comment, all comments on it, all comments on these comments and so far from the conversation because all these comments on comments no longer have a parent, and therefore, they no longer have anywhere to attach in the conversation.

If you delete the post, you delete the whole conversation. The comments on the post will no longer have a parent, and nothing in the conversation will have a post to refer to anymore.

#Long #LongPost #CWLong #CWLongPost #FediMeta #FediverseMeta #CWFediMeta #CWFediverseMeta #Mastodon #Friendica #Hubzilla #Streams #(streams) #Forte #Conversationa

@nutomic I solved this by having an the instance be an actor that is an intermediary for all operations. All activities get CC'ed to the followers of the user actor, and of the instance actor. (replace instance with community/group, whatever you use as an aggregate element for your implementation)

This should cover all interested parties imho.

The potential downside is that instances need to explicitly operate between themselves with follow operations (which conveniently also solves the problem of unwanted interactions with less savory corners of the fediverse).

Like I said, a problem of addressing.

@nutomic I realize this explanation probably skips a lot of information that's clear to me from my context, but I'll try to answer if anyone has any questions.

mariusor@metalhead.club that works too!

thisismissem seems I misspoke, as Nutomic's reply above clarifies: the tree stays but is effectively orphaned. Lemmy v1.0 will allow the reply tree to be accessed post-deletion.

The original query does still remain the same: what would be the best way forward to explicitly signal the deletion (or technically, the removal) of an entire reply tree?

cc jdp23@neuromatch.social mariusor@metalhead.club

@julian @jdp23 well, a Delete can be operated on an array of objects.

Send one with all the objects that are affected from the local instance (and probably you must keep in mind that not all replies might be).

I do agree that with_replies, or similar, would be the easiest approach, but I don't think it is the most specific.

The bool suggests that all replies to a given object are deleted. However, you do not know whether your idea of what the reply tree is matches that of the originating server (which replies are included, etc.?)

Remove(Context), on the other hand does imply both that the container is deleted, and all of its replies, which are dereferenceable by resolving the context directly. It also has the benefit of being able to provide a pointer to where it was removed from, which is useful.

So to me it's not just a matter of preference, but that there are additional benefits to Remove

I will of course concede that it is more work to deliver Remove.

cc thisismissem

mariusor@metalhead.club let's ask helge@mymath.rocks what implementor support for Delete(Array) looks like LOL

@julian as long as it's in the spec, I don't really care.

If we all bow to inferior implementations the ecosystem will stagnate. Mastodon's quirks have done enough damage in my opinion. My choice is to be brave and build for the future.

PS. Not to brag or anything () but my implementation can operate on activities with arrays as object, actor, etc.

One thing where you can lead the way (because the threadiverse would really benefit from it) is to accept arrays in inReplyTo (where you put all the ancestors of the current post, not just the parent).

@helge

I'm sure that approach works as well. This would have been worth discussing 4 or 5 years ago when I was just implementing federation in Lemmy for the first time. By now FEP-1b12 is already an established standard which is used by various platforms, and it would be completely unfeasible to replace it with something else.

I fail to see what the fundamental difference is. If you are unsure about the target with Delete/Object, you can also resolve the context of Object to figure that out. Anyway the instance where the Group is hosted is always the authority, so the state there is the correct one.

Actually I would rather think of this from a different perspective, namely from the perspective of the mod who clicks the remove button. That would happen when a post is offtopic or violates the rules, and then the intent clearly is to remove all replies as they are not useful. It wouldnt make sense to leave up a single reply two levels deep just because it wasnt included in the context for some reason.

@julian This sounds like an implementation detail to me. Some fedi platforms delete a child object when its parent is deleted, others don't.

If you want to make the removal of a subtree explicit, I'd recommend a Remove where object is an array (similar to what @mariusor suggested):

Remove(object: Note[], target: Context)

This also helps with migrating away from Announce(Delete). I saw your FEP draft, will provide more feedback once I read it in full.

@rimu @nutomic @melroy @BentiGorlich

@nutomic if you're implying that I should have spoken sooner, I'm pretty sure I did. I remember exchanging messages with both you and @dessalines when you started lemmy...

I have no specific memory about this topic, but to my recollection lemmy federation was pushed as fait-accomplit at one point without me seeing any previous research on your guys part.

silverpill@mitra.social mm I may have been premature regarding phasing out Announce(Delete).

nutomic@lemmy.ml made it clear that it wasn't going anywhere, and I will remove the "backwards compatibility" label from it in my draft.

Back then I didnt understand federation so well yet, so its possible that I didnt get what you were saying. And once I got the federation working there wasnt much reason to redo it in a different way which would effectively do the same thing.

@thisismissem @nutomic it's not a JSON-LD thing. it's the lack of schematic constraint within the Activity Vocabulary. any property not defined as "functional" can have more than one value.

@mariusor @julian @helge i don't think "all the ancestors" makes sense for inReplyTo. by doing that, you are claiming that your post is a response to every post in the thread above it. multiple inReplyTo still makes sense but should be used only where you are actually responding to certain things. if you want ancestors, define a property "ancestors" which is a list of ancestors ordered in a specific way (like in the mastodon api)