Steve Bate
What if... you had one Fedi account on a generic headless #ActivityPub server that simply hosts and federates your data... and had C2S UIs for microblogging, long form writing, media editing and sharing, link aggregation, games, fitness tracking, and so on, that all used that same Fedi account. Technically, it's a similar concept as ATProto (but no relay and app view) and Solid Pods (but no RDF).
It seems possible... if we can improve the AP C2S API/protocol sufficiently.
Evan Prodromou
@steve I believe in this mission.
silverpill
@steve If by "sufficiently improve" you mean throwing it away and replacing with a better protocol, then yes it's possible.
Evan Prodromou
@lutindiscret @steve this is built into ActivityPub and has been since the start.
Lutin Discret
@steve this is a reason why blue sky made a new protocol. Tu support that first day. Fedi will take 20 years to do that
Evan Prodromou
I can't wait to see what you build! Good luck.
Evan Prodromou
Silverpill does not agree with us. I am wishing Silverpill well in their plan to rebuild with a completely different API. Silverpill is skilled and smart and very familiar with ActivityPub in great detail, so I'm sure they will come up with some interesting API architecture.
Evan Prodromou
@raphael @silverpill @steve I also think that Steve's vision is realisable with ActivityPub API, although I think adding optional features like search, server push and so on makes it easier.
Raphael Lullis
Maybe I am way over my head, but this seems like *exactly* what I am building right now and I'm not really building anything outside of ActivityPub C2S?
I mean... Yes, my current client assumes some specific profile for OAuth and the client will need a proxy to get some data remote servers (to bypass authorized fetch, or to resolve documents from transient activities), but doesn't seem to me that anything I am doing is outside of AP's scope?
Evan Prodromou
@raphael @silverpill @steve I don't intend to stop working on the ActivityPub API.
There are a lot of us collaborating through the SocialCG ActivityPub API Task Force, and I expect that collaboration to continue:
Evan Prodromou
@mariusor @steve Does your server work with https://checkin.swf.pub/ ? Or https://github.com/evanp/ap ?
marius
@steve I've built the server part already, that was 5 years ago. Still waiting for people with the skills to build the UIs though...
Matthias Pfefferle
@evan @mariusor @steve oh neat!
https://matthiaspfefferle.blog/2026/02/25/checked-in-at-ettlingen/
https://github.com/Automattic/wordpress-activitypub/pull/2977
Evan Prodromou
@pfefferle @mariusor @steve WHAT
Evan Prodromou
@pfefferle @mariusor @steve that's awesome!
silverpill
@evan @raphael @steve I think a generic ActivityPub server can't be built without major changes to ActivityPub. For example, it might be necessary to make all side-effects of activities explicit.
And there is a bigger problem. A generic server without FEP-ef61 is like ATProto PDS or Nostr relay but all data is tied to a single server. This means that it is obsolete before the work has even begun.
silverpill
@steve @evan @raphael A server can't properly process an arbitrary activity without knowing its side effects. A server that only supports a small number of activities mentioned in the ActivityPub spec is obviously not generic.
I can point to other challenges because I've been working on this problem for years, but...
Several generic AP server implementations have been built
There are also simpler ways to design servers so that content isn't tied to a specific server
Wow, for real? I suppose it's time for me to retire then.
Steve Bate
@silverpill @evan @raphael Several generic AP server implementations have been built, so I don't know what you mean by the side-effect comment. Note that my mental model of a generic server doesn't implement any domain-specific behaviors in the server, but only side-effects specified by AP (and extended generic C2S support). There are also simpler ways to design servers so that content isn't tied to a specific server (with different tradeoffs than FEP-ef61). That's a long discussion...
silverpill
@mariusor @steve @evan @raphael
I don't see any reason to call this a generic server if it doesn't support extensions. Just a headless server that implements AP C2S
marius
@silverpill I think you're getting confused about ActivityPub side-effects and application logic side-effects.
I call my project FedBOX a "Generic ActivityPub server" because outside of storing ActivityPub objects and activities to a local storage and dispatching said activities to their recipients it doesn't do anything else.
However there's nothing preventing someone from forking the project and adding some other type of logic to it for specific combinations of Activities/Objects. That's the thing I'm trying to do with my GoActivityPub library: take care of the ActivityPub stuff, so you can then do your own stuff alongside it.
silverpill
@mariusor @steve @evan @raphael An extension is a protocol extension. Specifically, I talked about activity types that are not mentioned in ActivityPub.
Here is a side effect of a Like activity:
The side effect of receiving this in an outbox is that the server SHOULD add the object to the actor's liked Collection.
Now imagine that you have an EmojiReact activity which server should add to object's emojiReactions collection as a side-effect.
A generic server should be able to do that.
marius
@silverpill what are extensions exactly? Are you talking about FEPs that proscribe behaviour alongside structure, or ActivityPub extensions as allowed by JSON-LD.
The FEPs that proscribe behaviour can't ever be done in a "generic" way, and I'm betting you already know that and you're just being facetious.
However the JSON-LD dynamic structure can be reasoned about generically from an ActivityPub point of view using the points I made above: storage to disk, dispatch to recipients.
If you plug smart clients on top of that that have the specific logic you want, you're all the way there to what Steve was talking about.
Evan Prodromou
@silverpill @mariusor @steve @raphael
I think it's a fair critique and one that we should deal with.
However, I think it's possible to provide value where the server implements side effects of AP core, and not for any other Activity Vocabulary activities or extensions.
With the core AP activities, we can probably give clients most of what they need to implement "side effects" for extensions.
Evan Prodromou
@silverpill @mariusor @steve @raphael
For example, let's say we decide that an `Arrive` activity should update the `location` property of the actor.
`Arrive` isn't a core activity in AP. So, instead of expecting the server to change the `location`, the client can send an additional `Update` activity to change the actor's `location` itself.
With CRUD activities and collection activities in core we can get a lot of this done from the client side.
Evan Prodromou
@silverpill @mariusor @steve @raphael
I think there's value in having a negotiation between the client and the server so the server can declare its support for side effects for extensions. A way for the server to say, "I'll handle side effects for geosocial applications". Then the client can skip implementing those side effects itself.
Evan Prodromou
@silverpill @mariusor @steve @raphael
All that said, I think we can get pretty far with the core AP activities with defined side effects, and extension activities with "side effects" implemented by the client.
Evan Prodromou
@silverpill @mariusor @steve @raphael
More powerful would be a way for clients or actors to define side effect rules for servers dynamically. "If you get an Arrive activity, set the actor's location."
silverpill
@steve By side effect I mean anything that is not directly expressed in the activity, and EmojiReact usually doesn't specify that emojiReactions collection should be updated.
Add(object=EmojiReact, target=object_emojiReactions)? A generic server could support that.
Yes, this is what I said in the beginning of this sub-thread. All side-effects should be made explicit (at least for non-standard activities).
Steve Bate
@silverpill @mariusor @evan @raphael "you have an EmojiReact activity which server should add to object's emojiReactions collection as a side-effect."
It's a direct rather than side effect, but how is that different from Add(object=EmojiReact, target=object_emojiReactions)? A generic server could support that.
Evan Prodromou
@silverpill @raphael @steve I think that comes down to what you mean by "support".
I think a server that delivers extension activities, or activities with extension properties or extension types as `object` etc , locally or remotely, is "supporting" those types.
Implementing server-side side effects of some extensions may be a bonus, but we can build a lot of great stuff without it.
silverpill
@raphael @steve @evan It relates to ActivityPub API because ActivityPub is described as an extensible protocol. If a server doesn't support "extensions", it is not a generic server.
Raphael Lullis
I don't follow: how does that relate to the "ActivityPub API" if the activity is "arbitrary" and not defined by ActivityPub, not using AS2 vocabulary?
Isn't that like saying that we can't use HTTP as a protocol because an HTTP server doesn't know what to do with verbs defined on, e.g, WebDAV?
silverpill
@raphael @mariusor @steve @evan Your example is incorrect because activity types are not like HTTP verbs. Like and EmojiReact are part of the same protocol, both are widely used in Fediverse. Not sure what is the point of twisting the meaning of words to make limitations of certain software appear as non-limitations.
Raphael Lullis
I'm really not following this logic: you are saying "a generic HTTP server should be able to serve WebDAV requests".
Yes, HTTP servers should be able to serve WebDAV requests, *provided* they implement the extension.
It doesn't mean that they *have* to implement the extension. And an HTTP server that does not support the extension does not make non-HTTP compliant.
Evan Prodromou
flo
Evan Prodromou
@mariusor I'll check it!
marius
Hey @evan ... I've looked into why I get issues with checkin.swf.pub, and it could be that I'm doing something wrong, but it hits my servers using client_id=https://checkin.swf.pub/client.jsonld
Which, when gets dereferenced serves an ActivityPub Actor(ish) like document instead of the Client ID Metadata I'm expecting.
I remember I was arguing with Emelia about how to server both formats from the same URL, but in the end I decided it's not worth my time trying to do both, and I'm just expecting the data model described in the RFC7591 Sect2: https://datatracker.ietf.org/doc/html/rfc7591#section-2
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.