32 research outputs found

    On the Hardness of Bribery Variants in Voting with CP-Nets

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    We continue previous work by Mattei et al. (Mattei, N., Pini, M., Rossi, F., Venable, K.: Bribery in voting with CP-nets. Ann. of Math. and Artif. Intell. pp. 1--26 (2013)) in which they study the computational complexity of bribery schemes when voters have conditional preferences that are modeled by CP-nets. For most of the cases they considered, they could show that the bribery problem is solvable in polynomial time. Some cases remained open---we solve two of them and extend the previous results to the case that voters are weighted. Moreover, we consider negative (weighted) bribery in CP-nets, when the briber is not allowed to pay voters to vote for his preferred candidate.Comment: improved readability; identified Cheapest Subsets to be the enumeration variant of K.th Largest Subset, so we renamed it to K-Smallest Subsets and point to the literatur; some more typos fixe

    Probabilistic Conditional Preference Networks (UAI 2013)

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    International audienceThis paper proposes a \probabilistic" extension of conditional preference networks as a way to compactly represent a probability distributions over preference orderings. It studies the probabilistic counterparts of the main reasoning tasks, namely dominance testing and optimisation from the algorithmical and complexity viewpoints. Efficient algorithms for tree-structured probabilistic CP-nets are given. As a by-product we obtain a lineartime algorithm for dominance testing in standard, tree-structured CP-nets

    The computational complexity of dominance and consistency in CP-Nets

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    We investigate the computational complexity of testing dominance and consistency in CP-nets. Previously, the complexity of dominance has been determined for restricted classes in which the dependency graph of the CP-net is acyclic. However, there are preferences of interest that define cyclic dependency graphs; these are modeled with general CP-nets. In our main results, we show here that both dominance and consistency for general CP-nets are PSPACE-complete. We then consider the concept of strong dominance, dominance equivalence and dominance incomparability, and several notions of optimality, and identify the complexity of the corresponding decision problems. The reductions used in the proofs are from STRIPS planning, and thus reinforce the earlier established connections between both areas.

    Finding optimal alternatives based on efficient comparative preference inference

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    Choosing the right or the best option is often a demanding and challenging task for the user (e.g., a customer in an online retailer) when there are many available alternatives. In fact, the user rarely knows which offering will provide the highest value. To reduce the complexity of the choice process, automated recommender systems generate personalized recommendations. These recommendations take into account the preferences collected from the user in an explicit (e.g., letting users express their opinion about items) or implicit (e.g., studying some behavioral features) way. Such systems are widespread; research indicates that they increase the customers' satisfaction and lead to higher sales. Preference handling is one of the core issues in the design of every recommender system. This kind of system often aims at guiding users in a personalized way to interesting or useful options in a large space of possible options. Therefore, it is important for them to catch and model the user's preferences as accurately as possible. In this thesis, we develop a comparative preference-based user model to represent the user's preferences in conversational recommender systems. This type of user model allows the recommender system to capture several preference nuances from the user's feedback. We show that, when applied to conversational recommender systems, the comparative preference-based model is able to guide the user towards the best option while the system is interacting with her. We empirically test and validate the suitability and the practical computational aspects of the comparative preference-based user model and the related preference relations by comparing them to a sum of weights-based user model and the related preference relations. Product configuration, scheduling a meeting and the construction of autonomous agents are among several artificial intelligence tasks that involve a process of constrained optimization, that is, optimization of behavior or options subject to given constraints with regards to a set of preferences. When solving a constrained optimization problem, pruning techniques, such as the branch and bound technique, point at directing the search towards the best assignments, thus allowing the bounding functions to prune more branches in the search tree. Several constrained optimization problems may exhibit dominance relations. These dominance relations can be particularly useful in constrained optimization problems as they can instigate new ways (rules) of pruning non optimal solutions. Such pruning methods can achieve dramatic reductions in the search space while looking for optimal solutions. A number of constrained optimization problems can model the user's preferences using the comparative preferences. In this thesis, we develop a set of pruning rules used in the branch and bound technique to efficiently solve this kind of optimization problem. More specifically, we show how to generate newly defined pruning rules from a dominance algorithm that refers to a set of comparative preferences. These rules include pruning approaches (and combinations of them) which can drastically prune the search space. They mainly reduce the number of (expensive) pairwise comparisons performed during the search while guiding constrained optimization algorithms to find optimal solutions. Our experimental results show that the pruning rules that we have developed and their different combinations have varying impact on the performance of the branch and bound technique

    Conflicting Objectives in Decisions

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    This book deals with quantitative approaches in making decisions when conflicting objectives are present. This problem is central to many applications of decision analysis, policy analysis, operational research, etc. in a wide range of fields, for example, business, economics, engineering, psychology, and planning. The book surveys different approaches to the same problem area and each approach is discussed in considerable detail so that the coverage of the book is both broad and deep. The problem of conflicting objectives is of paramount importance, both in planned and market economies, and this book represents a cross-cultural mixture of approaches from many countries to the same class of problem

    A Method for Evidence Based Quality Practice Engineering

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    Ohjelmistotuotannon laatu on yhä yksi IT-teollisuuden suurimpia ongelmia. Erityisen kiinnostava kysymys on, kuinka tietty laatutaso voitaisiin saavuttaa systemaattisesti. Empiirinen ohjelmistotuotanto (EBSE) pyrkii vastaamaan tähän kysymykseen keräämällä todistusaineistoa aitojen ohjelmistotuotantoprosessien ja -tuotoksien toimivuudesta. Tässä työssä tutkimusnäkökulmaksi on valittu laatukäytäntöjen ja -tavoitteiden välinen suhde konstruoimalla ja vertailemalla uusia menetelmä ohjelmistotuotantoprosessien kehittämiseksi. Tutkimusta varten suoritettiin yhteensä viisi toimintotutkimuksellista ja konstruktiivista interventiota neljässä suomalaisessa keskikokoisessa ohjelmistotuote-yrityksessä. Ensiksi sovellettiin laatupalettianalyysi -menetelmää kolmessa yrityksessä. Tämän jälkeen konsturoitiin uudet indikaattorianalyysi ja "NMA"-aivomyrsky menetelmät. Viimeisenä konstruktiona rakennettiin semanttisen verkon -teknologiaan pohjautuva tietämyskanta laatutavoitteiden ja -käytäntöjen välisten vaikutusten tutkimiseen. Tutkimuksen tulokset ovat kaksiosaiset. Huolimatta siitä, että todistusaineiston määrällisen puutteen takia tilastollisesti merkittäviä tuloksia ei voida tässä työssä esittää, uusi tietämyskanta vaikuttaisi teoreettisesti pystyvän tutkituista menetelmistä ainoana vastaamaan tutkimuskysymyksessä esitettyyn kysymykseen. Teollisuuden lisäksi tietämyskantaa on mahdollista hyödyntää akateemisessa tutkimuksessa, opetuksessa, koulutuksessa ja ohjelmistotuotantoprosessin kehitysideoiden arvioinnissa. Tietämyskanta pystyi vastaamaan tiettyihin kysymyksiin, kuten "mitä käytäntöjä tulisi soveltaa varmistuakseen, ettei ohjelmistopäivitykseen kuluva työmäärä ylitä 8h:a?". Vastauksena saatiin käytäntövektori "savutestiasennus" ja "alfa/beta -testaus". Vähäisen tutkimustiedon takia tietämyskanta ei kuitenkaan pysty toistaiseksi vastaamaan esimerkiksi miten päivitykseen kuluvaa työmäärää voitaisiin lyhentää. Lisäksi tuloksen luotettavuutta voidaan pitää heikkona. Tietokannan antamien vastauksien laajuutta ja luotettavuutta voitaisiin kuitenkin helposti parantaa laatimalla systemaattisia kirjallisuuskatsauksia kaikesta saatavilla olevasta ohjelmistotuotantokäytäntöihin liittyvästä tieteellisestä kirjallisuudesta ja syöttämällä tulokset tietämyskantaan. Kunnes tietämyskannasta pystytään kehittämään teolliseen käyttöön soveltuva versio, NMA -aivomyrsky on selkeästi tehokkain menetelmä kehitysideoiden tuottamiseen. Muut tutkitut työpajamenetelmät eivät aina tuottaneet lainkaan kehitysideoita eivätkä siten sovellu teolliseen käyttöön. Kuitenkin tämän työn lopussa esitetään ehdotuksia siitä, kuinka laatupalettianalyysiä voitaisiin hyödyntää tietämyskannan tiedonkeruumenetelmänä mm. poistamalla työpaja-vaihe ja kehittämällä uusi esitehtävätyökalu.The quality of the software has been and remains as a key problem of the software industry. Especially interesting questions is, how a certain level of quality can be systematically reached. Evidence-based software engineering (EBSE) tries to provide answer to this question by collecting empirical evidence on different aspects of the software engineering process and deliverables. In this work the perspective of quality practices and goals has been selected for constructing and evaluating a method that could be used for industrial software process improvement (SPI). Four subject Finnish middle-sized software product companies were studied by performing in total five action research and constructive interventions. First the novel Quality Palette Analysis -method was applied for three subject companies in different variations. Next the Indicator Analysis and the New Method A (NMA) -brainstorming method were constructed and applied by the author. As a final constructive step, the author designed a novel Semantic Web -based EBSE experience factory for mapping the empirical evidence on the relationship of the quality goals and practices. The results of the study are two-fold. While the collected data on the relationship between the quality goals and practices remains insufficient to draw definitive claims, it seems that the EBSE DB provides theoretically a very high utility model for software process improvement (SPI) initiative evaluation, training & education, and for the scientific research. The database is able to answer questions such as "which practices should be used to ensure reaching of effort of 8h per update" with an answer vector of practices "smokeTesting" and "alphaBetaTesting". Due to small amount of samples the database is currently unable to answer for example, how an update effort of 1 hour less could be reached and the results can be considered unreliable. However, the reliability and range of answerable questions could be easily improvement by performing systematic literature review on all available scientific evidence on the software engineering practices. While such a system remains as a prototype, the NMA -brainstorming method provided clearly the best yield of SPI initiatives compared to the time invested in the data collection. The other methods were by the best cumbersome and can't be recommended for industrial application in their current forms. However, the author provides suggestions how the QPA-method could be altered to function in the Future as a primary data collection method for the EBSE DB in context of individual companies by omitting the workshop -phase and developing an automatic data collection tool similar to the current QPA pre-assignment

    Evolutionary multi-objective decision support systems for conceptual design

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    Merged with duplicate record 10026.1/2328 on 07.20.2017 by CS (TIS)In this thesis the problem of conceptual engineering design and the possible use of adaptive search techniques and other machine based methods therein are explored. For the multi-objective optimisation (MOO) within conceptual design problem, genetic algorithms (GA) adapted to MOO are used and various techniques explored: weighted sums, lexicographic order, Pareto method with and without ranking, VEGA-like approaches etc. Large number of runs are performed for findingZ Dth e optimal configuration and setting of the GA parameters. A novel method, weighted Pareto method is introduced and applied to a real-world optimisation problem. Decision support methods within conceptual engineering design framework are discussed and a new preference method developed. The preference method for translating vague qualitative categories (such as "more important 91 , 4m.9u ch less important' 'etc. ) into quantitative values (numbers) is based on fuzzy preferences and graph theory methods. Several applications of preferences are presented and discussed: * in weighted sum based optimisation methods; s in weighted Pareto method; * for ordering and manipulating constraints and scenarios; e for a co-evolutionary, distributive GA-based MOO method; The issue of complexity and sensitivity is addressed as well as potential generalisations of presented preference methods. Interactive dynamical constraints in the form of design scenarios are introduced. These are based on a propositional logic and a fairly rich mathematical language. They can be added, deleted and modified on-line during the design session without need for recompiling the code. The use of machine-based agents in conceptual design process is investigated. They are classified into several different categories (e. g. interface agents, search agents, information agents). Several different categories of agents performing various specialised task are developed (mostly dealing with preferences, but also some filtering ones). They are integrated with the conceptual engineering design system to form a closed loop system that includes both computer and designer. All thesed ifferent aspectso f conceptuale ngineeringd esigna re applied within Plymouth Engineering Design Centre / British Aerospace conceptual airframe design project.British Aerospace Systems, Warto
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