144,386 research outputs found
The Complexity of Online Manipulation of Sequential Elections
Most work on manipulation assumes that all preferences are known to the
manipulators. However, in many settings elections are open and sequential, and
manipulators may know the already cast votes but may not know the future votes.
We introduce a framework, in which manipulators can see the past votes but not
the future ones, to model online coalitional manipulation of sequential
elections, and we show that in this setting manipulation can be extremely
complex even for election systems with simple winner problems. Yet we also show
that for some of the most important election systems such manipulation is
simple in certain settings. This suggests that when using sequential voting,
one should pay great attention to the details of the setting in choosing one's
voting rule. Among the highlights of our classifications are: We show that,
depending on the size of the manipulative coalition, the online manipulation
problem can be complete for each level of the polynomial hierarchy or even for
PSPACE. We obtain the most dramatic contrast to date between the
nonunique-winner and unique-winner models: Online weighted manipulation for
plurality is in P in the nonunique-winner model, yet is coNP-hard (constructive
case) and NP-hard (destructive case) in the unique-winner model. And we obtain
what to the best of our knowledge are the first P^NP[1]-completeness and
P^NP-completeness results in the field of computational social choice, in
particular proving such completeness for, respectively, the complexity of
3-candidate and 4-candidate (and unlimited-candidate) online weighted coalition
manipulation of veto elections.Comment: 24 page
A Sound and Complete Axiomatization of Majority-n Logic
Manipulating logic functions via majority operators recently drew the
attention of researchers in computer science. For example, circuit optimization
based on majority operators enables superior results as compared to traditional
logic systems. Also, the Boolean satisfiability problem finds new solving
approaches when described in terms of majority decisions. To support computer
logic applications based on majority a sound and complete set of axioms is
required. Most of the recent advances in majority logic deal only with ternary
majority (MAJ- 3) operators because the axiomatization with solely MAJ-3 and
complementation operators is well understood. However, it is of interest
extending such axiomatization to n-ary majority operators (MAJ-n) from both the
theoretical and practical perspective. In this work, we address this issue by
introducing a sound and complete axiomatization of MAJ-n logic. Our
axiomatization naturally includes existing majority logic systems. Based on
this general set of axioms, computer applications can now fully exploit the
expressive power of majority logic.Comment: Accepted by the IEEE Transactions on Computer
School algebra and the computer
How are we to use the computer in the teaching and learning of algebra? In the longterm
the new technology is introducing new possibilities that may radically change the
algebra curriculum. However, in the short-term we already have the National
Curriculum placing its template on the development of algebra in school. The recent
regrouping of topics into five attainment targets has integrated number pattern with the
development of algebraic symbolism. It seems natural to build from expressing patterns
in words to expressing them in a shorthand algebraic notation, but, although this
proves a sound tactic for the more able, there are subtle difficulties for the majority of
children. Instead I shall advocate introducing algebraic symbolism by using it as a
language of communication with the computer, through programming in a suitable
computer language. This has two distinct benefits â it develops a meaningful algebraic
language which can be used to describe number patterns, and it gives a foundation for
traditional algebra and its manipulation
X THEN X: Manipulation of Same-System Runoff Elections
Do runoff elections, using the same voting rule as the initial election but
just on the winning candidates, increase or decrease the complexity of
manipulation? Does allowing revoting in the runoff increase or decrease the
complexity relative to just having a runoff without revoting? For both weighted
and unweighted voting, we show that even for election systems with simple
winner problems the complexity of manipulation, manipulation with runoffs, and
manipulation with revoting runoffs are independent, in the abstract. On the
other hand, for some important, well-known election systems we determine what
holds for each of these cases. For no such systems do we find runoffs lowering
complexity, and for some we find that runoffs raise complexity. Ours is the
first paper to show that for natural, unweighted election systems, runoffs can
increase the manipulation complexity
Computer-Aided Conceptual Design Through TRIZ-based Manipulation of Topological Optimizations
Organised by: Cranfield UniversityIn a recent project the authors proposed the adoption of Optimization Systems [1] as a bridging element
between Computer-Aided Innovation (CAI) and PLM to identify geometrical contradictions [2], a particular
case of the TRIZ physical contradiction [3].
A further development of the research has revealed that the solutions obtained from several topological
optimizations can be considered as elementary customized modeling features for a specific design task. The
topology overcoming the arising geometrical contradiction can be obtained through a manipulation of the
density distributions constituting the conflicting pair. Already two strategies of density combination have been
identified as capable to solve geometrical contradictions.Mori Seiki â The Machine Tool Compan
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