(2023-11-06) Berjon Activitypub Over Atproto

Robin Berjon on ActivityPub Over ATProto. With relatively little work, we could run ActivityPub atop an AT Protocol PDS.

The first thing to understand is that the AT Protocol is not Bluesky. ATProto is intended to be a generic toolbox for building social media applications, and it arguably extends (or can readily be extended) beyond that into supporting general infrastructure for a Personal Data Server (PDS). In fact, the ATProto architecture is explicitly described in terms of a PDS and of that PDS being a user agent. While Bluesky have been clear that they intend to keep control over the app.bsky API routes that implement Bluesky atop ATProto, they have also been clear that the com.atproto routes are intended to be an open standard.

ATProto has interesting properties, notably in how it supports pluggable identity that doesn't depend on the server you use as well as signed data repositories.

This puts power in the hands of the users and not (as is the case with vanilla federation) in those of server admins

ATProto on its own doesn't do any social media. It's "just" a layer atop of which protocols can be implemented.

Success? Not quite.

if we can just run ActivityPub over ATProto with just a bit of JSON tinkering and an ATProto app, without changing either spec. The answer is: not quite, but it's not so far as to be unbridgeable or even impractical.