Mercoledì 11 Maggio 2016, ore 15:30 ​presso la Sala Amministrazione (Sapienza Università di Roma, Dipartimento MEMOTEF, Via del Castro Laurenziano 9, Roma - Facoltà di Economia, 4° piano)

Nathanael Barrot (Ph.D. Lamsade, Paris-Dauphine University, France)

terrà un seminario dal titolo: Computation and Manipulation of Approval Voting for Committee elections

ABSTRACT:
Approval voting is a well-known voting procedure used, among others, for electing committees, where each voter casts a ballot consisting of a set of approved candidates. Two prominent rules for electing committees using approval voting are the standard rule (also called minisum), which selects the set of candidates (possibly subject to some cardinality constraint) with the highest number of approvals, and the minimax rule, where the set of elected candidates minimizes the maximum, over all voters, of the Hamming distance to the voter's ballot. As these two rules are in some way too extreme, we generalize them into a continuum of rules, by using ordered weighted averaging operators (OWA). The rules are parameterized by a weight vector W, which allows us to model voting procedures between minisum and minimax. We address the computational aspects of finding a winning committee and the issue of manipulating those rules. Furthermore, we study a more general setting, namely approval voting in combinatorial domains, where voters are allowed to express conditional preferences. New methods are suggested for how to use approval voting in this context.