[messaging] Partial order group chat with partial history visibility

[Ximin Luo]

Ximin Luo:
> Jeff Burdges:
>>
>> Is there even a global partial order G for typical DVCs for example?
>> It's just the local ones that actually exist on disk, right?  
>>
> 
> Yes, that is G the "full history".
> 

One thing to note here is that I don't mean that everyone *has already received G*. What I mean is the union of all events that everyone has committed to their local copies.

Everything I've said so far, has nothing to do with "who has received which events/commits"; which is already well-handled by the fact that we're representing everything as a partial order. What I am talking about is *permission to read*.

In DVCS and other applications, this union of all events G is in theory readable by everyone, via the "clone" or "pull" operations. These applications don't need to deal with "partial visibility": everyone that can read the same set X of messages, can also read all of its ancestors (that ever existed), and this is the same set of ancestors.

Not so with "partial history", which is a scenario specific to private group chats, and I haven't come across it before in any other setting, either academic or in software.

X

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