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From "Bruno Gonzalez (aka stenyak)" <sten...@gmail.com>
Subject Re: Future of Apache wave [Was: Re: Advantages of P2P messaging?]
Date Wed, 12 Jun 2013 17:59:42 GMT
```This sounds *awfully* similar to darcs patch theory. If the concepts are
the same, then all the theory is already worked out if i'm not mistaken.
http://en.wikibooks.org/wiki/Understanding_Darcs/Patch_theory#Merging_is_symmetric
http://darcs.net/Theory

On Wed, Jun 12, 2013 at 7:39 PM, Joseph Gentle <josephg@gmail.com> wrote:

> Did you meet Torben at the wave summit? He took me through his way to
> mitigate this problem. He describes it briefly here:
>
> In short, give every operation a unique hash. Each peer stores its own
> (transformed) history list.
>
> When two peers sync with each other, they need to figure out which
> operations they are each missing (still not sure what the best way to
> do this is). They send missing operations to one another, with some
> context.
>
> Locally, imagine I've applied:
> X A' B' C
> and I want to sync with a peer which has ops:
> A B D
> ... Obviously, I need to apply D locally. But I don't have an X' that
> I can transform D by! We can solve this by rewriting our history.
>
> So Torben came up with the idea of a prune function (inverse
> transform). Then we can define:
>
> swap = (a, b) ->
>   b' = prune(b, a)
>   a' = transform(a, b')
>
> I can use that to take my local history:
> X A' B' C
> and swap X past A B to get:
> A B X' C
> Then I can transform D by X' C to get D', that I can apply locally.
>
> I don't need to re-save the new operation history if I don't want to -
> A B X' C D' is just as valid as X A B C D'. I think there's some
> clever decisions we can make there to decrease the number of
> transforms that the network will need to perform.
>
> I made a proof-of-implementation last week, and it works & converges.
> (It was really exciting, even though Torben beat me to the punch a
> couple of years ago):
> https://github.com/josephg/tp2stuff/blob/master/node.coffee
>
> -J
>
>
> On Wed, Jun 12, 2013 at 9:38 AM, Michael MacFadden
> > Other ways to mitigate this are interesting areas of research.
> >
> >
> > ~Michael
>

--
Saludos,
Bruno González

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Jabber: stenyak AT gmail.com
http://www.stenyak.com

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