Lexicon Reference

Open Social uses AT Protocol lexicons to define the data structures stored in community PDS repositories.

community.opensocial.profile

The community’s public profile, stored at rkey self.

{
  "$type": "community.opensocial.profile",
  "displayName": "My Community",
  "description": "A place for discussion",
  "type": "open",
  "guidelines": "Be kind and respectful",
  "avatar": { "$type": "blob", "ref": { "$link": "..." }, "mimeType": "image/jpeg" },
  "banner": { "$type": "blob", "ref": { "$link": "..." }, "mimeType": "image/jpeg" },
  "createdAt": "2025-01-01T00:00:00.000Z"
}

Field	Type	Description
displayName	string	Community name (max 64 chars)
description	string	Short description (max 512 chars)
type	string	open, admin-approved, or private
guidelines	string	Community rules (max 3000 chars)
avatar	blob	Community avatar image
banner	blob	Community banner image
createdAt	datetime	When created

community.opensocial.admins

Admin list, stored at rkey self. The first entry is the primary (original) admin.

{
  "$type": "community.opensocial.admins",
  "admins": [
    { "did": "did:plc:creator123", "addedAt": "2025-01-01T00:00:00.000Z" },
    { "did": "did:plc:admin456", "addedAt": "2025-01-15T00:00:00.000Z" }
  ]
}

Field	Type	Description
admins	array	List of admin objects
admins[].did	string	Admin’s DID
admins[].addedAt	datetime	When added as admin

community.opensocial.membership

Stored in the user’s PDS repo. Indicates intent to join a community.

{
  "$type": "community.opensocial.membership",
  "community": "did:plc:community123",
  "joinedAt": "2025-01-01T00:00:00.000Z"
}

Field	Type	Description
community	string	Community DID
joinedAt	datetime	When the user joined

community.opensocial.membershipProof

Stored in the community’s PDS repo. Confirms a user is a verified member.

{
  "$type": "community.opensocial.membershipProof",
  "memberDid": "did:plc:user123",
  "cid": "bafyrei...",
  "confirmedAt": "2025-01-01T00:00:00.000Z"
}

Field	Type	Description
memberDid	string	Member’s DID
cid	string	CID of the user’s membership record
confirmedAt	datetime	When membership was confirmed

Dual-Record Model

A complete membership requires both records:

• membership in user’s repo → user wants to be a member
• membershipProof in community’s repo → community confirms membership

membership	membershipProof	Status
✅	✅	Active member
✅	❌	Removed or not yet approved
❌	✅	User has left

community.opensocial.list

A named list within a community.

{
  "$type": "community.opensocial.list",
  "name": "Book Recommendations",
  "community": "did:plc:community123",
  "createdBy": "did:plc:user123",
  "createdAt": "2025-01-01T00:00:00.000Z",
  "description": "Great books to read"
}

community.opensocial.listitem

An item in a community list.

{
  "$type": "community.opensocial.listitem",
  "list": { "uri": "at://did:plc:community/community.opensocial.list/abc", "cid": "bafyrei..." },
  "item": { "uri": "at://did:plc:user/app.bsky.feed.post/xyz", "cid": "bafyrei..." },
  "addedBy": "did:plc:user123",
  "addedAt": "2025-01-01T00:00:00.000Z"
}