{"type":"ScholarlyArticle","title":"Choosing Collectively Optimal Sets of Alternatives Based on the Condorcet Criterion","authors":[{"name":"Edith Elkind","slug":"edith-elkind","given":"Edith","family":"Elkind","affiliation":""},{"name":"Jérôme Lang","slug":"jerome-lang","given":"Jérôme","family":"Lang","affiliation":""},{"name":"Abdallah Saffidine","slug":"abdallah-saffidine","given":"Abdallah","family":"Saffidine","affiliation":""}],"abstract":"In elections, an alternative is said to be a Condorcet winner if it is preferred to any other alternative by a majority of voters. While this is a very attractive solution concept, many elections do not have a Condorcet winner. In this paper, we propose a setvalued relaxation of this concept, which we call a Condorcet winning set: such sets consist of alternatives that collectively dominate any other alternative. We also consider a more general version of this concept, where instead of domination by a majority of voters we require domination by a given fraction theta of voters; we refer to this concept as theta-winning set. We explore social choice-theoretic and algorithmic aspects of these solution concepts, both theoretically and empirically.","doi":"10.5591/978-1-57735-516-8/IJCAI11-042","url":"https://ijcai.org/proceedings/2011/42","pdf":"https://ijcai.org/proceedings/2011/0042.pdf","markdown":"https://ijcai.org/proceedings/2011/42.md","bibtex":"https://ijcai.org/proceedings/2011/bibtex/42","volume":{"slug":"2011","title":"Proceedings of the Twenty-Second International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2011","url":"https://ijcai.org/proceedings/2011/","year":2011,"location":"Barcelona, Catalonia, Spain","dates":"16–22 July 2011","editors":"Toby Walsh","isbn":"978-1-57735-512-0; 978-1-57735-513-7; 978-1-57735-514-4; 978-1-57735-515-1; 978-1-57735-516-8","publisher":"AAAI Press/International Joint Conferences on Artificial Intelligence","doi_prefix":""},"section":null,"track":"","number":42,"pages":{"first":186,"last":190},"keywords":[],"videos":[],"references":[],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}