Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.

Requirement

Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.

Origin

The origin of this requirement is a quote from the ActivityPub specfiication:
prefixIf a recipient is a Collection or OrderedCollection, then the server MUST dereference the collection (with the user's credentials) and discover inboxes for each item in the collection.
Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.
suffix Servers MUST de-duplicate the final recipient list.
https://www.w3.org/TR/activitypub/ , § 7.1

id

urn:uuid:7eb4f1aa-5779-4935-9840-f2909a5c6d70

uuid

7eb4f1aa-5779-4935-9840-f2909a5c6d70

Full JSON

{
  "id": "urn:uuid:7eb4f1aa-5779-4935-9840-f2909a5c6d70",
  "uuid": "7eb4f1aa-5779-4935-9840-f2909a5c6d70",
  "type": "Behavior",
  "content": "Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.\n",
  "tag": [
    {
      "name": "ActivityPubServer",
      "id": "https://socialweb.coop/tag/ActivityPubServer"
    }
  ],
  "context": [
    "https://www.w3.org/TR/activitypub/",
    {
      "name": "7. Server to Server Interactions",
      "id": "https://www.w3.org/TR/activitypub/#server-to-server-interactions"
    },
    {
      "name": "7.1 Delivery",
      "id": "https://www.w3.org/TR/activitypub/#delivery"
    }
  ],
  "origin": {
    "source": "https://www.w3.org/TR/activitypub/",
    "section": {
      "id": "https://www.w3.org/TR/activitypub/#delivery",
      "branch": [
        7,
        1
      ]
    },
    "selector": {
      "type": "TextQuoteSelector",
      "prefix": "If a recipient is a Collection or OrderedCollection, then the server MUST dereference the collection (with the user's credentials) and discover inboxes for each item in the collection.\n",
      "exact": "Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.\n",
      "suffix": "Servers MUST de-duplicate the final recipient list.\n"
    }
  },
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://socialweb.coop/ns/testing/context.json"
  ]
}

Links