Bug#727708: TC resolution revised draft
On Fri, Jan 31, 2014 at 03:02:21PM +0100, Sébastien Villemot wrote:
> Le vendredi 31 janvier 2014 à 11:55 +0000, Neil McGovern a écrit :
> > On Fri, Jan 31, 2014 at 09:33:33AM +0100, Josselin Mouette wrote:
> > > Given the Condorcet voting method is susceptible to tactical voting,
> >
> > Hi Josselin,
> >
> > I'm not sure what you mean here, could you care to elaborate?
>
> Here is my understanding of the issue, on a simplified example.
>
> Let's restrict to the following 4 options from the last draft ballot:
>
> DT systemd default in jessie, requiring specific init is allowed
> DL systemd default in jessie, requiring specific init NOT allowed
>
> UT upstart default in jessie, requiring specific init is allowed
> UL upstart default in jessie, requiring specific init NOT allowed
>
> And let's suppose that the CTTE has 4 members: P1 (the chairman), P2, P3
> and P4. Let's suppose that the vote is as follows:
>
> P1: DT > UT > DL > UL
> P2: DL > UL > DT > UT
> P3: UT > UL > DL > DT
> P4: UT > UL > DL > DT
>
> P1 and P2 both prefer systemd over upstart, while P3 and P4 prefer
> upstart over systemd. But P1 and P2 disagree on the coupling question (T
> versus L), while P3 and P4 agree with each other.
>
> The Condorcet winner of this vote is UT (and note that the casting vote
> of P1 is not needed here, since UT is alone in the Schwartz set).
>
> This result is not necessarily what one would have expected beforehand.
> In particular, if the ballot had not included the options about
> coupling, then systemd would have won because of the casting vote of the
> chairman.
>
> Fundamentally, the reason of the victory of upstart in this hypothetical
> vote is that systemd proponents prefer to lose on the coupling question
> rather than on the init system question, while the upstart proponents
> have the opposite preference over the relative importance of these two
> questions.
>
> Of course, in the alternative scenario with two consecutive ballots (one
> on the init, followed by one on the coupling), it would not have been
> possible to express this preference over the relative importance of the
> two questions, so one could argue that this is a feature of the single
> ballot with all options.
>...
I would argue your example shows the voters not understanding how the
voting system works...
Quoting the Debian Constitution:
Options which the voters rank above the default option are options
they find acceptable. Options ranked below the default options are
options they find unacceptable.
If in your example P1 and P2 would both rank FD (the default option
"further discussion") second, then DL wins.
And if additionally P3 and P4 would rank FD second or third, then FD wins.
The casting vote of the chairman sounds more powerful than it is in
actually, since in any situation between two options where no option has
a majority of at least the quorum, each side can prevent the other side
from winning.
So if for example 4 members of the TC would say "only systemd is an
acceptable choice", and the other 4 members of the TC would say "only
upstart is an acceptable choice", then any result other than "further
discussion" would be caused by a voting error.
And this is not a problem of the Condorcet voting system, this is due to
the explicit statement "There is a quorum of two." in the Constitution.
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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