Matrix: a new specification for federated realtime chat

The main algorithmic difference with Inkblot is that Matrix's federated message history is all cryptographically signed by the originating server (to avoid tampering over open federation), and is built on a replicated directed acyclic graph datastructure to provide eventual consistency semantics and elegantly handle netsplits, data loss, etc. It's obviously intended for realtime messaging, whereas NNTP isn't exactly up to the job of IM or VoIP signalling. And Matrix syncs arbitrary JSON rather than MIME envelopes. It's true that Matrix is slightly inspired by NNTP (as well as IRC, IMAP, eventually consistent DBs, etc). (I'm the tech lead on Matrix, fwiw).