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FEP-f15d: Context Relocation and Removal (#749)
Co-authored-by: Julian Lam <julian@nodebb.org> Reviewed-on: https://codeberg.org/fediverse/fep/pulls/749 Co-authored-by: devnull <devnull@noreply.codeberg.org> Co-committed-by: devnull <devnull@noreply.codeberg.org>
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devnull
silverpill
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---
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slug: "f15d"
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authors: Julian Lam <julian@nodebb.org>, Felix Ableitner <me@nutomic.com>, Rimu Atkinson <rimu@rimu.geek.nz>
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status: DRAFT
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dateReceived: 2026-01-12
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discussionsTo: https://activitypub.space/topic/86/fep-f15d-context-relocation-and-removal
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---
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# FEP-f15d: Context Relocation and Removal
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## Summary
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Threaded applications often have the need to move and remove content between groups/communities for curation purposes (i.e. resolving miscategorization, spam, etc.)
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This is an extension of the [Resolvable Contexts][7888] tree of FEPs.
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## Requirements
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC-2119].
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## Assumptions
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### Nomenclature
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The Forums and Threaded Discussions Task Force (ForumWG) has [identified a common nomenclature][Nomenclature] when referring to organized objects in a threaded discussion model. The two terms used in this FEP are described below:
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#### Context
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A group of related objects (i.e. via reply-association) is referred to as a "context". Other terms for this concept would be "topic" or "thread".
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#### Audience
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Contexts (see above) can be further grouped together into "audiences". Other terms for this concept would be "community", "category", or "forum". In ActivityPub, audiences usually take the form of a [`Group` Actor type][GroupActor].
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### Referencing threaded objects as a whole
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ActivityPub implementations differ in how they represent the aggregated collection of threaded objects.
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Some implementations represent these collections as a distinct abstraction (e.g. a context.)
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Others make no such distinction and represent them via the root-level object (e.g. link aggregators.)
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The resolvable contexts tree of FEPs _requires_ that abstraction in order to communicate actions pertaining to it in an explicit manner.
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For more information, see [FEP 7888][7888].
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## Relocation
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When a publisher relocates a context from one audience to another, a `Move` activity is published to both audiences' followers.
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``` json
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{
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@context: "https://www.w3.org/ns/activitystreams",
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id: "https://example.social/context/123#activity/move/<timestamp>",
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type: "Move",
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actor: "https://example.social/uid/1",
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to: ["https://www.w3.org/ns/activitystreams#Public"],
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cc: [
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"https://example.social/audience/1/followers",
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"https://example.social/audience/2/followers",
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],
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object: "https://example.social/context/1",
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origin: "https://example.social/audience/1",
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target: "https://example.social/audience/2",
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}
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```
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Note the following properties:
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* `actor` is the user actor carrying out the action; typically a moderator (see [Security Considerations](#security))
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* `cc` contains the follower collections of both the outgoing and incoming audiences
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* `object` is the resolvable context
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* `origin` is the outgoing audience
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* `target` is the incoming audience
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* Additional recipients can and should be added as necessary (e.g. originating author, announcers, etc.)
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### `Audience` wrapper
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Implementations MAY wrap the `Move` activity in an `Announce` activity. Receivers are recommended to support both types.
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## Removal
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There are two ways to signal that a context is removed from an audience.
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>[!NOTE]
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> A **removal** is functionally different from a **deletion**. You cannot delete content that is originally from another server, as you are not the owner, but you _are_ able to remove it from yours.
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### Resolvable context variant
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When a publisher removes a context from an audience, a `Remove` activity is published to the audience's followers.
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``` json
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{
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@context: "https://www.w3.org/ns/activitystreams",
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id: "https://example.social/context/123#activity/remove/<timestamp>",
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type: "Remove",
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actor: "https://example.social/uid/1",
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to: ["https://www.w3.org/ns/activitystreams#Public"],
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cc: ["https://example.social/audience/1/followers"],
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object: "https://example.social/context/1",
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target: "https://example.social/audience/1",
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}
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```
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### Group federation variant
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_This sub-section is non-normative_
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Implementations may also handle the federated removal of objects by federating out a `Delete` referencing the root-level object. This activity is further wrapped in an `Announce` activity per [FEP 1b12][1b12].
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``` json
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{
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"actor": "http://ds9.lemmy.ml/u/lemmy_alpha",
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"to": ["https://www.w3.org/ns/activitystreams#Public"],
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"object": "http://ds9.lemmy.ml/post/1",
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"cc": ["http://enterprise.lemmy.ml/c/main"],
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"audience": "http://enterprise.lemmy.ml/u/main",
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"type": "Delete",
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"id": "http://ds9.lemmy.ml/activities/delete/f2abee48-c7bb-41d5-9e27-8775ff32db12"
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}
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```
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_Example from [Join Lemmy: Section 30 "Federation" — "Delete Post or Comment"][LemmyDelete]_
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<a id="security"></a>
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## Security Considerations
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### Same-Origin Check
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As per [FEP fe34][OriginBasedSecurityModel], the `Remove` and `Move` events outlined in this FEP are assumed to be authentic if the actor and the audience(s) in question (`target` and if applicable, `origin`) are same-origin.
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### Moderator Collection Check
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[FEP-1b12: Group federation][1b12] describes the use of an `OrderedCollection` referenced in an audience's `attributedTo` [to represent an audience's moderators](https://codeberg.org/fediverse/fep/src/branch/main/fep/1b12/fep-1b12.md#group-moderation).
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If the actor of the `Move` or `Remove` activities is not same-origin to the audience(s) in question, this collection SHOULD be cross-referenced for authorization.
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## Implementors
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* NodeBB (as of v4.7.0)
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* Piefed (as of v1.5)
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## References
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- Christine Lemmer-Webber, Jessica Tallon, Erin Shepherd, Amy Guy, Evan Prodromou, [ActivityPub], 2018
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- James M Snell, Evan Prodromou, [Activity Vocabulary](https://www.w3.org/TR/activitystreams-vocabulary), 2017
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- a, [FEP 7888: Demystifying the context property][7888], 2023
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- Julian Lam, [ForumWG Nomenclature][Nomenclature], 2024
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- Felix Ableitner, [FEP-1b12: Group federation][1b12], 2022
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- Join Lemmy: Section 30 "Federation" — ["Delete Post or Comment"][LemmyDelete]
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- silverpill, [FEP fe34][OriginBasedSecurityModel]: Origin-based security model
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[ActivityPub]: https://www.w3.org/TR/activitypub/
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[7888]: https://w3id.org/fep/7888
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[1b12]: https://w3id.org/fep/1b12
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[Nomenclature]: https://github.com/swicg/forums/issues/4
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[LemmyDelete]: https://join-lemmy.org/docs/contributors/05-federation.html#delete-post-or-comment
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[OriginBasedSecurityModel]: https://w3id.org/fep/fe34
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[GroupActor]: https://www.w3.org/TR/activitystreams-vocabulary/#dfn-group
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## Copyright
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
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To the extent possible under law, the authors of this Fediverse Enhancement Proposal have waived all copyright and related or neighboring rights to this work.
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