Dan,

Does this mean that the wave servers are doing intention preserving in their
OT implementation? I haven't seen where that is implemented in the FedOne
released code base...

brett

On Tue, Dec 1, 2009 at 4:41 PM, Daniel Paull <[email protected]> wrote:

>
> A small correction.  I said, "all sites will agree that the result is
> either "16" or that the result is "17", regardless of the order in
> which they apply the operations."
>
> I should have said that all sites will agree that the result is
> either "167" or that the result is "176", regardless of the order in
> which they apply the operations.
>
> Note - I have assumed that each client deleted and inserted only one
> character.
>
> Dan
>
>
> Daniel Paull wrote:
> > Hi Jelke,
> >
> > I assume you mean that the operations by the two clients are performed
> > concurrently.  You are right in your thinking that the transformation
> > is ambiguous - this is where OT starts to get tricky!
> >
> > Please refer the OT Functions section of the OT page on Wikipedia:
> >
> >     http://en.wikipedia.org/wiki/Operational_transformation#OT_Functions
> >
> > which I will repoduce below:
> >
> >     T(ins(p1,c1,sid1),ins(p2,c2,sid2)) :-
> >       if (p1 < p2) return ins(p1,c1,sid1)
> >       else if (p1 = p2 and sid1 < sid2) return ins(p1,c1,sid1)
> >       else return ins(p1 + 1,c1,sid1)
> >
> > Notice that when the insertion positions of two concurrent insert
> > operations are equal (ie, when p1 = p2), the function resorts to
> > comparing site identifiers, sid1 and sid2.  It is required that site
> > identifiers are globally unique and have a total ordering.  Now the OT
> > function is unambiguous and all sited will agree that the result is
> > either "16" or that the result is "17", regardless of the order in
> > which they apply the operations.
> >
> > Now, I'm not sure exactly what Wave does regarding site identifiers,
> > but I am sure that the above strategy will be used.
> >
> >
> > Cheers,
> >
> > Dan
> >
> >
> > On Nov 29, 10:05 pm, "Jelke  J. van Hoorn" <[email protected]> wrote:
> > > Hi,
> > >
> > > I was looking the "under the hood" vidieo of Google IO 2009. And I'm
> > > wondering what happens in the following situation:
> > >
> > > On the server a piece of text is lets say "15" and two clients alter
> > > the same piece in "16" and "17" respectively.
> > > What would be the outcome of the transforms? There is no unambigeous
> > > way to cope with this edit I think.
> > >
> > > Grtz Jelke
>
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-- 
Brett Morgan http://domesticmouse.livejournal.com/

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