2023-01-24

Activity Streams graphical model

Johannes Ernst

https://reb00ted.org/tech/20230124-activitystreams-model/

All you need is a gazillionaire doing strange things to some internet platform, and all of a sudden decentralized social media soars in adoption. So lots of people are suddenly seriously looking at how to contribute, myself included.

Core to this is the ActivityPub standard, and real-world implementations that mix it with additional independently defined protocols, such as what Mastodon does.

None of them are particularly easy to understand. So I did a bit of drawing just to make it clearer (for myself) what kind of data can be shipped around in the Fediverse. To be clear, this is only a small part of the overall stack, but an important one.

Here are some diagrams. They are essentially inheritance diagrams that show what kinds of activities there are, and actors, etc. Posted here in case they are useful for others, too.

And here’s how to interpret my homegrown graphical notation. (I made it up for my dissertation eons ago, and used it ever since. It has certain advantages over, say, UML or traditional ERA diagram styles. IMHO :-))