219 research outputs found
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Preference-Based Characterizations of Truthfulness and the Limited Expressiveness of Order-Based Domains
An important direction in computational mechanism design is to characterize the space of choice functions that can be truthfully implemented. For this, one must carefully describe the class of preferences in a domain. For unrestricted preferences the domain is well-characterized, and small. Moreover, recent work [Lavi et al., 2003] has allowed for “order-based” preferences but found essentially the same (negative) characterization. However, most interesting domains have preferences that are still more structured than those allowed in the orderbased model. We highlight this issue in our paper, through many examples, thus demonstrating the limited applicability of this result. We propose extensions to the model of order-based domains to capture new preference structure, and conjecture that more positive characterizations for truthfulness are possible. We also advocate, in proposing a research direction for sufficient conditions for truthfulness, that attention be restricted to natural (critical-value based) payment functions.Engineering and Applied Science
Interdependent Public Projects
In the interdependent values (IDV) model introduced by Milgrom and Weber
[1982], agents have private signals that capture their information about
different social alternatives, and the valuation of every agent is a function
of all agent signals. While interdependence has been mainly studied for
auctions, it is extremely relevant for a large variety of social choice
settings, including the canonical setting of public projects. The IDV model is
very challenging relative to standard independent private values, and welfare
guarantees have been achieved through two alternative conditions known as {\em
single-crossing} and {\em submodularity over signals (SOS)}. In either case,
the existing theory falls short of solving the public projects setting.
Our contribution is twofold: (i) We give a workable characterization of
truthfulness for IDV public projects for the largest class of valuations for
which such a characterization exists, and term this class \emph{decomposable
valuations}; (ii) We provide possibility and impossibility results for welfare
approximation in public projects with SOS valuations. Our main impossibility
result is that, in contrast to auctions, no universally truthful mechanism
performs better for public projects with SOS valuations than choosing a project
at random. Our main positive result applies to {\em excludable} public projects
with SOS, for which we establish a constant factor approximation similar to
auctions. Our results suggest that exclusion may be a key tool for achieving
welfare guarantees in the IDV model
New bounds for truthful scheduling on two unrelated selfish machines
We consider the minimum makespan problem for tasks and two unrelated
parallel selfish machines. Let be the best approximation ratio of
randomized monotone scale-free algorithms. This class contains the most
efficient algorithms known for truthful scheduling on two machines. We propose
a new formulation for , as well as upper and lower bounds on
based on this formulation. For the lower bound, we exploit pointwise
approximations of cumulative distribution functions (CDFs). For the upper
bound, we construct randomized algorithms using distributions with piecewise
rational CDFs. Our method improves upon the existing bounds on for small
. In particular, we obtain almost tight bounds for showing that
.Comment: 28 pages, 3 tables, 1 figure. Theory Comput Syst (2019
Partial Verification as a Substitute for Money
Recent work shows that we can use partial verification instead of money to
implement truthful mechanisms. In this paper we develop tools to answer the
following question. Given an allocation rule that can be made truthful with
payments, what is the minimal verification needed to make it truthful without
them? Our techniques leverage the geometric relationship between the type space
and the set of possible allocations.Comment: Extended Version of 'Partial Verification as a Substitute for Money',
AAAI 201
Truthful ownership transfer with expert advice: Blending mechanism design with and without money
When a company undergoes a merger or transfers its ownership, the existing governing body has an opinion on which buyer should take over as the new owner. Similar situations occur while assigning the host of big sports tournaments, like the World Cup or the Olympics. In all these settings, the values of the external bidders are as important as the opinions of the internal experts. Motivated by such scenarios, we consider a social welfare maximizing approach to design and analyze truthful mechanisms in {\em hybrid social choice} settings, where payments can be imposed to the bidders, but not to the experts. Since this problem is a combination of mechanism design with and without monetary transfers, classical solutions like VCG cannot be applied, making this a novel mechanism design problem. We consider the simple but fundamental scenario with one expert and two bidders, and provide tight approximation guarantees of the optimal social welfare. We distinguish between mechanisms that use ordinal and cardinal information, as well as between mechanisms that base their decisions on one of the two sides (either the bidders or the expert) or both. Our analysis shows that the cardinal setting is quite rich and admits several non-trivial randomized truthful mechanisms, and also allows for closer-to-optimal welfare guarantees
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