Group
ActivityStreams §4.1"type": "Group"
Group represents a collection of actors that can receive and forward activities to members. Used by Lemmy communities, Friendica groups, and Hubzilla forums. When a Group receives a Create activity in its inbox, it announces (boosts) the activity to all followers, acting as a community hub for topic-based discussion.
Details
Group actors are the foundation of community-style federation in the Fediverse. Unlike Person actors (individual users), Groups aggregate content from multiple contributors and broadcast it to followers.
Group behavior in Lemmy: - Every Lemmy community is a Group actor - Users post to a Group by addressing the Create activity to the Group - The Group receives the post in its inbox and Announces it to all Group followers - This is the federation mechanism that lets Mastodon users follow and post to Lemmy communities
Forum semantics: Lemmy, Friendica, and Hubzilla use Group actors for forum-style threaded discussions. The Group inbox acts as a thread aggregator.
Group vs Person for communities: - Mastodon uses Person actors for hashtag relay accounts (bots that boost hashtag posts) - Lemmy uses Group actors for communities with proper member-to-community posting semantics - The choice affects which clients display the actor as a community vs a user
Required Fields
| @context | "https://www.w3.org/ns/activitystreams" |
| type | "Group" |
| id | Permanent HTTPS URL for this group |
| inbox | HTTPS URL of inbox (where members POST activities) |
| outbox | HTTPS URL of outbox OrderedCollection |
Common Optional Fields
| name | Group display name |
| summary | Group description |
| followers | OrderedCollection of group members/subscribers |
| attributedTo | Creator/owner of the group |
Examples
{
"@context": "https://www.w3.org/ns/activitystreams",
"type": "Group",
"id": "https://lemmy.world/c/technology",
"name": "Technology",
"summary": "<p>General technology discussion</p>",
"inbox": "https://lemmy.world/c/technology/inbox",
"outbox": "https://lemmy.world/c/technology/outbox",
"followers": "https://lemmy.world/c/technology/followers"
}// User sends Create activity addressed to Group
{
"type": "Create",
"actor": "https://mastodon.social/users/alice",
"to": ["https://lemmy.world/c/technology"],
"object": {
"type": "Note",
"content": "Check out this new programming language!",
"to": ["https://lemmy.world/c/technology"]
}
}
// Group receives, validates, then Announces to all followers