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Often times people ask me, "But how do I learn about how ActivityPub works? Where do I get started?"

Friends! The ActivityPub spec itself is here to help you! There's a really lovely story-driven tutorial about ActivityPub right at the top of the spec in the "Overview" section! w3.org/TR/activitypub/#Overvie

Give it a read! I tried really hard to make it easy to follow, and it has beautiful illustrations from @mray!

www.w3.orgActivityPubThe ActivityPub protocol is a decentralized social networking protocol based upon the [ActivityStreams] 2.0 data format. It provides a client to server API for creating, updating and deleting content, as well as a federated server to server API for delivering notifications and content.
Gregg Kellogg

@cwebber @mray great use-case/intro to ActivityPub! If only the Verifiable Credentials WG would take to heart the spirit with which you describe json-ld. Extensibility and reusability are the whole point.