<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7653.38"> <TITLE>RE: [Sugar-devel] [ANNOUNCE] Groupthink 0.1 pre-alpha</TITLE> </HEAD> <BODY>  Hi Benjamin,             Thanks very much! I'm very interested in looking at the source code and data structures. These kind of problems are exactly what abicollab (as used by Write) solves. I have given some detailed presentations about this. You can find one here: (the ogg version) <A HREF="http://mirror.linux.org.au/pub/linux.conf.au/2008/Wed/mel8-083.ogg">http://mirror.linux.org.au/pub/linux.conf.au/2008/Wed/mel8-083.ogg</A> (presentation odp) <A HREF="http://mirror.linux.org.au/pub/linux.conf.au/2008/slides/083-AbiCollab.odp">http://mirror.linux.org.au/pub/linux.conf.au/2008/slides/083-AbiCollab.odp</A> and wiki write up: <A HREF="http://www.abisource.com/wiki/AbiCollab">http://www.abisource.com/wiki/AbiCollab</A> Maybe these ideas can help. Cheers! Martin -----Original Message----- From: sugar-devel-bounces@lists.sugarlabs.org on behalf of Benjamin M. Schwartz Sent: Thu 1/15/2009 3:25 PM To: Martin Edmund Sevior Cc: bens@alum.mit.edu; Sugar Devel; Chris Ball Subject: Re: [Sugar-devel] [ANNOUNCE] Groupthink 0.1 pre-alpha -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Martin Edmund Sevior wrote: >          How do you solve "internet lag". > > User A puts a character "A" in position 10, then before user B see sees this (because of the finite propagation time), he puts character "B" in position 10? > > Who wins? You just have to make sure the the document remains the same for both users. This is, indeed, the central problem.  For the moment, the answer is: Groupthink does not support full documents, only short snippets of text. I have prototyped a data structure that I believe can coherently resolve these sorts of edit conflicts in long documents without any negotiation, but it remains to be seen if the design will work. In general, Groupthink's approach (described at length in docstrings in the code) is to write each data structure in such a way that any two users who have observed the same set of messages will arrive at the same state, regardless of the order in which those messages are received.  The hard part is figuring out how to do this for each kind of data structure. However, once it is working, the code can be reused for many purposes without needing to understand how it works. - --Ben -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEARECAAYFAkluuskACgkQUJT6e6HFtqQb2QCfXnSJHwZpn6Q/OsDSs8nJEb3x vWIAoIJYuSuEp8EFOeKynHDLctW2S5iq =Po5R -----END PGP SIGNATURE----- _______________________________________________ Sugar-devel mailing list Sugar-devel@lists.sugarlabs.org <A HREF="http://lists.sugarlabs.org/listinfo/sugar-devel">http://lists.sugarlabs.org/listinfo/sugar-devel</A> </BODY> </HTML>