[messaging] Minimal requirements for group chat

Ximin Luo infinity0 at pwned.gg
Wed Apr 16 16:32:20 PDT 2014

On 16/04/14 23:38, Geoffroy Couprie wrote:
> Le 17 avr. 2014 00:27, "Daniel Kahn Gillmor" <dkg at fifthhorseman.net <mailto:dkg at fifthhorseman.net>> a écrit :
>> On 04/16/2014 06:19 PM, Geoffroy Couprie wrote:
>> > A git-like scheme with an elected master could make the transcript totally
>> > ordered. Basically, all the peers would receive the messages and still keep
>> > them in an unstaged area, partially ordered so still useful for the UI.
>> > Then the master would chime in and provide the definite  message order,
>> > kind of like a merge in git. The peers then reorder their transcript
>> > accordingly.
>> a merge in git does not produce a total order; i don't think this
>> proposal will work the way you think.
> How so? In that scheme, the master defines clearly the order (even if it is not the absolutely exact time based order).

Could you offer some more details? There are several things aren't considered in your short description.

- when would it be appropriate for the master to run this algorithm? what if he receives something "in the middle", after he has already decided the order?
- how would others display the "unstaged" items in the meantime?

I also don't think a merge is analogous to your scheme. Merges are done by clients themselves, and form part of the partial order, rather than turning it into a linear order.

>> I don't think a partial order is a bad thing, though.  a partial order
>> reflects the actual state of a distributed conversation; there's a
>> reason that mail user agents have traditionally offered a threaded view.
> The point is to get clients to agree on a transcript. Reflecting that transcript in the UI would be confusing since it would incur reodering. There could be a way to alert the user, though.
>>         --dkg


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