Differential Synchronization

Algorithm actually explained here:

    http://neil.fraser.name/writing/sync/

More about the theory can be found here:

    http://code.google.com/p/google-mobwrite/wiki/Theory

The talk is also here:

    http://neil.fraser.name/news/2009/01/11/

but has links to other stuff by the author. Recommended over the youtube link.

It would be interesting to run a real comparison between this, etherpad (http://www.etherpad.com) and CollabEdit (http://collabedit.com). I suspect that this is a problem everyone is trying to solve. Etherpad's extremely good, I've used it "in anger", but no doubt Google will win because it's Google.

I'm not yet sure whether the data in MobWrite is "public", but it is in EtherPad (if you can guess the URL).