Complexity results for preference aggregation over (m)CP-nets: Max and rank voting

Lukasiewicz, Thomas; Malizia, Enrico

doi:10.1016/j.artint.2021.103636

Cited by 4 publications

(2 citation statements)

References 38 publications

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“…One approach to preference aggregation using CP-nets is that of mCP-nets (Rossi, Venable, and Walsh 2004;Lukasiewicz and Malizia 2016, 2019, 2022. In this approach, the input is a set of partial CP-nets.…”

Section: Related Workmentioning

confidence: 99%

Approximation Algorithms for Preference Aggregation Using CP-Nets

Ali,

Yang,

Zilles

2024

AAAI

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This paper studies the design and analysis of approximation algorithms for aggregating preferences over combinatorial domains, represented using Conditional Preference Networks (CP-nets). Its focus is on aggregating preferences over so-called swaps, for which optimal solutions in general are already known to be of exponential size. We first analyze a trivial 2-approximation algorithm that simply outputs the best of the given input preferences, and establish a structural condition under which the approximation ratio of this algorithm is improved to 4/3. We then propose a polynomial-time approximation algorithm whose outputs are provably no worse than those of the trivial algorithm, but often substantially better. A family of problem instances is presented for which our improved algorithm produces optimal solutions, while, for any ε, the trivial algorithm cannot attain a (2- ε)-approximation. These results may lead to the first polynomial-time approximation algorithm that solves the CP-net aggregation problem for swaps with an approximation ratio substantially better than 2.

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Section: Related Workmentioning

confidence: 99%

Approximation Algorithms for Preference Aggregation Using CP-Nets

Ali,

Yang,

Zilles

2024

AAAI

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“…Also, it would be interesting to account for user preferences when answering queries, as recently done in [17,18], possibly considering other ways of expressing preferences, e.g. by means of CP-nets [19,20].…”

Section: Next Stepsmentioning

confidence: 99%

Querying Data Exchange Settings Beyond Positive Queries

Greco¹,

Molinaro²,

Trubitsyna³

2023

Theory and Practice of Logic Programming

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Data exchange, the problem of transferring data from a source schema to a target schema, has been studied for several years. The semantics of answering positive queries over the target schema has been defined in early work, but little attention has been paid to more general queries. A few proposals of semantics for more general queries exist but they either do not properly extend the standard semantics under positive queries, giving rise to counterintuitive answers, or they make query answering undecidable even for the most important data exchange settings, for example, with weakly-acyclic dependencies. The goal of this paper is to provide a new semantics for data exchange that is able to deal with general queries. At the same time, we want our semantics to coincide with the classical one when focusing on positive queries, and to not trade-off too much in terms of complexity of query answering. We show that query answering is undecidable in general under the new semantics, but it is $\text{co}\text{NP}\text{-complete}$ when the dependencies are weakly-acyclic. Moreover, in the latter case, we show that exact answers under our semantics can be computed by means of logic programs with choice, thus exploiting existing efficient systems. For more efficient computations, we also show that our semantics allows for the construction of a representative target instance, similar in spirit to a universal solution, that can be exploited for computing approximate answers in polynomial time.

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