@infinite love ⴳ Being able to filter incoming content is just as important as being able to receive it. Providing the categories and the thread would be useful for filtering.

For example, you might have a situation where a particular post may have the following information:

Owner = example.com/@forum
Author (of the post) = example.social/@user
Category = example.com/forum/category/activitypub
Thread = example.com/forum/post/12345

With this information, an inbox can be set up to show threads that are a specific category and ignore the rest. Or ignore certain authors without unfollowing the thread.

In this scenario, you would need to specify which is the thread and which is the category, because the conversation can be pulled from the thread, but not the category.

You can do the same thing with blog posts. Follow a blog, but only see blog posts with specific categories.

@evan @erincandescent @julian @mikedev @silverpill historical evidence that is also relevant here:

https://github.com/w3c/activitystreams/issues/300

https://github.com/w3c/activitystreams/issues/238#issuecomment-153408442

@scott Yes, correct. I think that the link relation (or semantic property relation) is what lets you do that. Imagine if instead of context/audience/tag/etc we just had a single property `itemOf` and it was just a grab-bag of every single collection that contained the current object. That wouldn't be very useful! So we use the semantic properties and we can filter against the semantic properties. Simply being in a collection is usually insufficiently semantic -- we need to specify how/why.

@scott Which is to say, an object can have:

- a `context` in which it exists and by which it should be grouped,
- an `audience` to which it is scoped and for which it can be considered relevant
- some `tag` to which it refers

The question is, what does a "category" represent semantically? If the "category" is an actor, then perhaps it is appropriate to say it is part of the `audience`. Otherwise, you might `tag` the "category" instead. Or you might define some other relation.

@trwnh @erincandescent @julian @mikedev @silverpill

> [...] unless you want everyone to manually join every single room one-at-a-time.

This has always been my experience with chat rooms. People join (or enter) the room, make posts to the room that are visible to everyone "in" the room, and some time -- maybe years later -- leave the room.

Regardless: groups and threads are not the same thing.

@trwnh @erincandescent @julian @mikedev @silverpill yes, `scope` became `audience` and was (incorrectly, I think) made into an addressing property in AP.

@evan @erincandescent @julian @mikedev @silverpill Joining a Discord guild (the Group, loosely) gives you access to multiple rooms/channels (a bunch of Collections) all at the same time. Each channel could be rendered as a chat room or as a forum thread or however you want to display a collection of objects.

Essentially, `audience` and `context` are converse properties. In many cases, the "group" is the `audience` and the "thread" is the `context`. This is emergent behavior in NodeBB/Discourse.

@evan @erincandescent @julian @mikedev @silverpill I suppose it could be complicated a bit when you start to consider rooms/channels/threads/topics/etc that are limited to a subset of the group/audience, for example via a roles system. But that's something I don't want to think about yet; at least not until we have a foundation that works for representing posts and contexts and audiences

@Evan Prodromou To put it another way, there are several levels.

1. Things you can join and follow, such as chat rooms, discussion groups, and forums. It has a membership, and the administrator controls who is a member and who is not. When you join, you automatically follow it.

2. Categorization and curation, such as tags, categories, lists, etc. This can be filtered against by the recipient. Or, if offered, can be followed.

3: Specific conversations, which can include forum threads, Facebook-style threads, direct message conversations, etc. This keeps conversations in a container so they are easier to read.

@infinite love ⴳ You cannot assume the audience is the same as the category, context, forum, or sender. Some software, such as Hubzilla, has access control. You can set the audience for each individual thread.

Also, what happens when a post has multiple contexts? It is part of a category that you can follow. It was placed in a curated list of posts that you can follow. And it is also part of a thread that is in a forum you can follow. You have three contexts and three actors for the same post.

If you are displaying posts (notes, articles, whatever) as part of a conversation, then knowing which one of those is the thread would be useful.

@scott objects can exist in multiple contexts, same as how an object can be in reply to multiple objects.

The part where I disagree is that not everything needs to be a `context`. A "category" is just a taxonomy, like any tag; the posts exist separately from that taxonomy. A "curated list of posts" is just a Collection, and the posts exist separately from that curated collection.

To figure out what is a context, ask: "does this post make sense on its own?" if no, it exists in some context.

@scott That is to say, the audience/category/context/forum/sender are all separate concepts. It's fine to set an audience for each thread separately. It's also fine to set an audience for each post separately. But if the post is meant to be viewed in the thread, then that thread is serving as a context. "Context" is loosely something that provides reason, purpose, understanding. It's got nothing to do with being in a collection or being followable (although a context MAY be those things.)

@infinite love ⴳ So, does that mean that context = thread, and nothing else can be a context?

@scott No, a thread is only a context if it's declared as an object's context. The context for an object should be something that gives it reason or purpose for existing; processing an object without its context means you aren't fully understanding the object. The context helps you understand that object.

This is generally a "conversation" but not always. Other examples of contextual grouping include a "project" or an "environment".

@scott Also note that a context doesn't have to be a Collection. You can group by anything. You could set `context` to a Person or Note or Event or whatever you want, if it helped you understand the current object, and if you grouped all objects that shared the same `context` (in a task list, for example). So it's like a tag, but with purpose. If there isn't a purpose, consider using a basic tag.

For "post" objects, it generally makes sense to use a Collection representing the "conversation".

@infinite love ⴳ So, what happens if a post is part of a thread and a project? How do you know which context is the thread?

My point is that a post can have more than one context.

@scott Right, so, if you have a specific meaning of "thread" in mind, then you can define a property for that. Would you say that a post can be part of more than one thread, or are you assuming a functional (max 1) relationship?

@infinite love ⴳ Traditionally, a post can only reside in one thread. If you try to assign a post to more than one thread, it breaks a lot of things, like the access list (audience) for the thread, moderation by administrators, etc. The "owner" of the thread (conversation container) becomes unclear if a post belongs to more than on thread.

That is probably why many people, including myself, want to define a thread as something separate from a collection.

So, I would say that a post can only reside in one thread, but can reside in multiple collections and/or contexts.

@scott Even if you define a thread property, that alone doesn’t stop someone from being able to declare multiple threads. I’m not convinced anyone can define “thread” in a way that is unique or even distinct from what we already have. Access lists are per-object, regardless of whether that object is a post or a collection of posts. You may be able to see a thread, but not all posts in that thread. Conversely, you may be able to see a post, but not the thread(s) it’s a part of.

@scott In any case, being part of a collection isn’t the same as having some context. Being part of a thread *usually* maps onto the concept of having additional context, where the thread provides context for the post, and the post exists in context of that thread. The way you handle context is by using it to group things. That context MAY have an owner, and it MAY be a collection. IF it has an owner, it is common courtesy to send your object to them. IF it is a collection, they may Add it.