[EM] "CDTT criterion" compliance desirable?

Chris Benham cbenhamau at yahoo.com.au
Tue Dec 23 04:35:10 PST 2008

In one of your recent papers and on the Schulze method Wikipedia
page you list  "Woodall's  CDTT criterion" as one of the criteria 
satisfied by the Schulze (Winning Votes) method.

What, in your opinion, is supposed to be the positive point of compliance
with that criterion? In other words, how would Schulze(WV) be worse
if it satisfied all the criteria presently on your list of satisfied criteria 
except that one?

Chris Benham

PS: For those who might not know, the "CDTT criterion" presumably
says that the winner must come from the CDTT set, explained below
by Kevin Venzke.


The CDTT is a set of candidates defined by Woodall to include every 
candidate A such that, for any other candidate B, if B has a majority-strength 
beatpath to A, then A also has a majority-strength beatpath back to B. 
(See Schulze for a definition of a beatpath.) Another definition (actually, the 
one Woodall chooses to use) of the CDTT is that it is the union of all minimal 
sets such that no candidate in each set has a majority-strength loss to any 
candidate outside this set. (Candidate A has a "majority-strength loss" to 
candidate B if v[b,a] is greater than 50% of the number of cast votes.)

Markus Schulze proposed this set earlier, in 1997. His wording was to take the 
Schwartz set resulting from replacing with pairwise ties, all pairwise wins with 
under a majority of the votes on the winning side.

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