[messaging] Minimal requirements for group chat

[Ximin Luo]

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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