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- Edith Hemaspaandra, Lane A. Hemaspaandra, Jörg Rothe
- AAAI
- 2005

Preference aggregation in a multiagent setting is a central issue in both human and computer contexts. In this paper, we study in terms of complexity the vulnerability of preference aggregation to destructive control. That is, we study the ability of an election’s chair to, through such mechanisms as voter/candidate addition/suppression/partition, ensure… (More)

- Piotr Faliszewski, Edith Hemaspaandra, Lane A. Hemaspaandra
- J. Artif. Intell. Res.
- 2009

We study the complexity of influencing elections through bribery: How computationally complex is it for an external actor to determine whether by a certain amount of bribing voters a specified candidate can be made the election’s winner? We study this problem for election systems as varied as scoring protocols and Dodgson voting, and in a variety of… (More)

For many election systems, bribery (and related) attacks have been shown NP-hard using constructions on combinatorially rich structures such as partitions and covers. This paper shows that for voters who follow the most central political-science model of electorates— single-peaked preferences—those hardness protections vanish. By using single-peaked… (More)

- Edith Hemaspaandra, Lane A. Hemaspaandra
- J. Comput. Syst. Sci.
- 2007

Scoring protocols are a broad class of voting systems. Each is defined by a vector (α1, α2, . . . , αm), α1 ≥ α2 ≥ · · · ≥ αm, of integers such that each voter contributes α1 points to his/her first choice, α2 points to his/her second choice, and so on, and any candidate receiving the most points is a winner. What is it about scoring-protocol election… (More)

- Patrick Blackburn, Edith Hemaspaandra
- Journal of Logic, Language and Information
- 1993

Much work has been devoted, during the past twenty years, to using complexity to protect elections from manipulation and control. Many results have been obtained showing NP-hardness shields, and recently there has been much focus on whether such worst-case hardness protections can be bypassed by frequently correct heuristics or by approximations. This paper… (More)

- Edith Hemaspaandra
- Notre Dame Journal of Formal Logic
- 1996

- Piotr Faliszewski, Edith Hemaspaandra, Lane A. Hemaspaandra
- Artif. Intell.
- 2011

Many electoral bribery, control, and manipulation problems (which we will refer to in general as "manipulative actions" problems) are NP-hard in the general case. It has recently been noted that many of these problems fall into polynomial time if the electorate is single-peaked (i.e., is polarized along some axis/issue). However, real-world electorates are… (More)

- Piotr Faliszewski, Edith Hemaspaandra, Henning Schnoor
- AAMAS
- 2008

We study the complexity of manipulation for a family of election systems derived from Copeland voting via introducing a parameter α that describes how ties in head-to-head contests are valued. We show that the thus obtained problem of manipulation for unweighted Copeland elections is NP-complete even if the size of the manipulating coalition is limited to… (More)

- Michael Bauland, Edith Hemaspaandra, Henning Schnoor, Ilka Schnoor
- STACS
- 2006

It is well known that modal satisfiability is PSPACEcomplete [Lad77]. However, the complexity may decrease if we restrict the set of propositional operators used. Note that there exist an infinite number of propositional operators, since a propositional operator is simply a Boolean function. We completely classify the complexity of modal satisfiability for… (More)