Old Unix hands will remember .plan and .project files, as well as the finger protocol.<p>ActivityPub, the social protocol on which Mastodon and other Fediverse systems are based, evolved from webfinger:<p><a href="https://en.wikipedia.org/wiki/WebFinger" rel="nofollow">https://en.wikipedia.org/wiki/WebFinger</a><p><a href="https://en.wikipedia.org/wiki/ActivityPub" rel="nofollow">https://en.wikipedia.org/wiki/ActivityPub</a>