The goal of this NIP is to create moderator-approved public communities around a topic. It defines the replaceable event `kind:34550` to define the community and the current list of moderators/administrators. Users that want to post into the community, simply tag any Nostr event with the community's `a` tag (See [NIP-33](33.md)). Moderators issue an approval event `kind:4550` that links the community with the new post.
`Kind:34550` SHOULD include any field that helps define the community and the set of moderators. `relay` tags MAY be used to describe the preferred relay to download requests and approvals.
Any Nostr event can be a post request. Clients MUST add the community's `a` tag to the new post event in order to be presented for the moderator's approval.
Community management clients MAY filter all mentions to a given `kind:34550` event and request moderators to approve each submission. Moderators MAY delete his/her approval of a post at any time using event deletions (See [NIP-09](09.md)).
The post-approval event MUST include `a` tags of the communities the moderator is posting into (one or more), the `e` tag of the post and `p` tag of the author of the post (for approval notifications). The event SHOULD also include the stringified `post request` event inside the `.content` ([NIP-18-style](18.md)) and a `k` tag with the original post's event kind to allow filtering of approved posts by kind.
It's recommended that multiple moderators approve posts to avoid deleting them from the community when a moderator is removed from the owner's list. In case the full list of moderators must be rotated, the new moderator set must sign new approvals for posts in the past or the community will restart. The owner can also periodically copy and re-sign of each moderator's approval events to make sure posts don't disappear with moderators.
Post Approvals of replaceable events can be created in three ways: (i) by tagging the replaceable event as an `e` tag if moderators want to approve each individual change to the repleceable event; (ii) by tagging the replaceable event as an `a` tag if the moderator authorizes the replaceable event author to make changes without additional approvals and (iii) by tagging the replaceable event with both its `e` and `a` tag which empowers clients to display the original and updated versions of the event, with appropriate remarks in the UI. Since relays are instructed to delete old versions of a replaceable event, the `.content` of an `e`-approval MUST have the specific version of the event or Clients might not be able to find that version of the content anywhere.
