diff --git a/app/changelog/page.mdx b/app/changelog/page.mdx
index 2bdb596..32ac559 100644
--- a/app/changelog/page.mdx
+++ b/app/changelog/page.mdx
@@ -17,6 +17,7 @@ This page lists changes since Working Draft 3. {{ className: 'lead' }}
- `X-Signed-By` to `Versia-Signed-By`
- Removed the nonce from the [signature system](/signatures), replaced with `Versia-Signed-At` (timestamps).
- Standardize rate limits with [IETF draft draft-polli-ratelimit-headers-02](https://www.ietf.org/archive/id/draft-polli-ratelimit-headers-02.html).
+- Properly documented [Group](/entities/group) federation and subscribing.
- Added [Versia Links](/links).
- Switched from ISO 8601 to [RFC 3339](https://datatracker.ietf.org/doc/html/rfc3339) for timestamps.
- In most cases, the two are interchangeable, but RFC 3339 is more strict. Most implementations should not need to change anything.
diff --git a/app/entities/group/page.mdx b/app/entities/group/page.mdx
index 7d19d25..2be98a1 100644
--- a/app/entities/group/page.mdx
+++ b/app/entities/group/page.mdx
@@ -24,6 +24,15 @@ Refer to [Note](/entities/note#entity-definition)'s `group` property for how not
Text only (`text/plain`, `text/html`, etc).
+
+ Whether the group is open to all users or requires approval to join.
+
+
+ **This is meant as a UI hint** and does not guarantee that group subscriptions will be accepted or rejected.
+
+ It is similar to a [User](/entities/user)'s `manually_approves_followers` field.
+
+
URI of the group's members list. [URI Collection](/structures/collection#uri-collection) of [Users](/entities/user).
@@ -50,9 +59,196 @@ Refer to [Note](/entities/note#entity-definition)'s `group` property for how not
"content": "A group for fans of the Woozy emoji."
}
},
+ "open": false,
"members": "https://example.com/groups/ed480922-b095-4f09-9da5-c995be8f5960/members",
}
```
+
+
+
+## Subscribing to Groups
+
+[Users](/entities/user) may "subscribe" to a Group in order to receive all [Notes](/entities/note) posted to it. The mechanism by which federation is handled is described at [the end of this document](#federation).
+
+First, a [User](/entities/user) must send a `GroupSubscribe` activity to the group. The group will then respond with either a `GroupSubscribeAccept` or a `GroupSubscribeReject` activity.
+
+If the group accepts the subscription, the user will receive all notes posted to the group. If the group rejects the subscription, the user will not receive any notes posted to the group.
+
+### GroupSubscribe
+
+Indicates that a [User](/entities/user) wishes to subscribe to a group.
+
+
+
+
+
+ This entity does not have a URI.
+
+
+ URI of the [User](/entities/user) subscribing to the group.
+
+
+ URI of the group to subscribe to.
+
+
+
+
+
+
+ ```jsonc {{ title: "Example GroupSubscribe" }}
+ {
+ "type": "GroupSubscribe",
+ "id": "9a7e9345-4e4a-4d5a-8301-4dbbfe777ca0",
+ "subscriber": "https://bob.social/users/e9277471-8aa1-4d40-a3d0-0878e818ccdc",
+ "group": "https://example.com/groups/ed480922-b095-4f09-9da5-c995be8f5960",
+ "created_at": "2021-01-01T00:00:00Z"
+ }
+ ```
+
+
+
+
+### GroupUnsubscribe
+
+Indicates that a [User](/entities/user) wishes to unsubscribe from a group.
+
+
+
+
+
+ This entity does not have a URI.
+
+
+ URI of the [User](/entities/user) unsubscribing from the group.
+
+
+ URI of the group to unsubscribe from.
+
+
+
+
+
+
+ ```jsonc {{ title: "Example GroupUnsubscribe" }}
+ {
+ "type": "GroupUnsubscribe",
+ "id": "9a7e9345-4e4a-4d5a-8301-4dbbfe777ca0",
+ "subscriber": "https://bob.social/users/e9277471-8aa1-4d40-a3d0-0878e818ccdc",
+ "group": "https://example.com/groups/ed480922-b095-4f09-9da5-c995be8f5960",
+ "created_at": "2021-01-01T00:00:00Z"
+ }
+ ```
+
+
+
+
+### GroupSubscribeAccept
+
+Indicates that a [Group](#entity-definition) has accepted a [User](/entities/user)'s subscription request. Should be signed by the instance hosting the group.
+
+
+
+
+
+ This entity does not have a URI.
+
+
+ URI of the [User](/entities/user) subscribing to the group.
+
+
+ URI of the group that accepted the subscription.
+
+
+
+
+
+
+ ```jsonc {{ title: "Example GroupSubscribeAccept" }}
+ {
+ "type": "GroupSubscribeAccept",
+ "id": "9a7e9345-4e4a-4d5a-8301-4dbbfe777ca0",
+ "subscriber": "https://bob.social/users/e9277471-8aa1-4d40-a3d0-0878e818ccdc",
+ "group": "https://example.com/groups/ed480922-b095-4f09-9da5-c995be8f5960",
+ "created_at": "2021-01-01T00:00:00Z"
+ }
+ ```
+
+
+
+
+### GroupSubscribeReject
+
+Indicates that a [Group](#entity-definition) has rejected a [User](/entities/user)'s subscription request. Should be signed by the instance hosting the group.
+
+
+
+
+
+ This entity does not have a URI.
+
+
+ URI of the [User](/entities/user) subscribing to the group.
+
+
+ URI of the group that rejected the subscription.
+
+
+
+
+
+
+ ```jsonc {{ title: "Example GroupSubscribeReject" }}
+ {
+ "type": "GroupSubscribeReject",
+ "id": "9a7e9345-4e4a-4d5a-8301-4dbbfe777ca0",
+ "subscriber": "https://bob.social/users/e9277471-8aa1-4d40-a3d0-0878e818ccdc",
+ "group": "https://example.com/groups/ed480922-b095-4f09-9da5-c995be8f5960",
+ "created_at": "2021-01-01T00:00:00Z"
+ }
+ ```
+
+
+
+
+## Federation
+
+Group federation represents a particularly challenging problem, as it requires a way to make sure every single [Note](/entities/note) posted to it is delivered to every single member of the group.
+
+All [Notes](/entities/note) posted to a group (using the `group` field) must be sent to its instance's [shared inbox](/federation#inboxes). Groups do not have an inbox of their own.
+
+Once this is done, the group's instance must then federate this [Note](/entities/note) to every member of the group. However, this cannot be done the "normal way", as the group's instance does not have the private key to [sign](/signatures) the [Note](/entities/note).
+
+### GroupFederate
+
+The `GroupFederate` entity allows a group to federate a note to all of its members, without needing to sign the note itself. It contains a URI to the note being federated, which must be fetched by the receiving instances. This entity is signed by the group's instance.
+
+
+
+
+
+ This entity does not have a URI.
+
+
+ URI of the note to federate.
+
+
+ URI of the group federating the note.
+
+
+
+
+
+
+ ```jsonc {{ title: "Example GroupFederate" }}
+ {
+ "type": "GroupFederate",
+ "id": "9a7e9345-4e4a-4d5a-8301-4dbbfe777ca0",
+ "note": "https://example.com/notes/ed480922-b095-4f09-9da5-c995be8f5960",
+ "group": "https://example.com/groups/ed480922-b095-4f09-9da5-c995be8f5960",
+ "created_at": "2021-01-01T00:00:00Z"
+ }
+ ```
+
\ No newline at end of file