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Bug#727708: TC resolution revised draft

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

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

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.

Still, my example shows that putting the two questions on the same
ballot is not just about letting people express different coupling
choices for different init systems. It can have the more fundamental
effect of changing the winning init system.

 .''`.    Sébastien Villemot
: :' :    Debian Developer
`. `'     http://www.dynare.org/sebastien
  `-      GPG Key: 4096R/381A7594

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