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Evidências empíricas de leilões na Internet: selos na eBay.; Empirical evidences from online auctions: stamps from eBay.

Villani Junior, Adhemar
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/11/2001 PT
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56.56%
Os leilões na Internet têm ganhado muita popularidade, tornando-se uma das mais bem sucedidas formas de comércio eletrônico na atualidade. Apresento um modelo teórico para descrever um leilão ascendente, semelhante ao que ocorre na eBay, e verifico suas previsões comportamentais através de dois experimentos. Os resultados mostraram um distanciamento grande entre as previsões teóricas e o que foi observado na prática, no que se refere às estratégias utilizadas, mas acredito que isso se deva à falta de experiência dos participantes dos experimentos. Desenvolvo, então, programas que automatizam a coleta de dados de leilões de selos na eBay e analiso as variáveis que influenciam preços, número de compradores e lances iniciais (preços mínimos). Não houve surpresas em tal análise, no sentido de observar-se resultados contra-intuitivos, mas destaco a reputação dos vendedores como fator relevante para a determinação de preços finais e número de compradores participantes. Além disso, também destaco a ocorrência da submissão tardia de lances, fenômeno recorrente nos leilões na Internet. Proponho, por fim, um método simples que busca determinar o tipo de modelo de leilão, se de valor comum ou de valor privado...

"Um processo para construção de frameworks a partir da engenharia reversa de sistemas de informação baseados na Web: aplicação ao domínio dos leilões virtuais" ; A Process for Framework Development from Reverse Engineering of Web-based Information Systems: Application to the Online Auction Domain

Ré, Reginaldo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/10/2002 PT
Relevância na Pesquisa
56.61%
Um processo para o desenvolvimento de frameworks para sistemas de informação baseados na Web é proposto. Esse processo é composto pelos subprocessos de engenharia reversa de sistemas baseados na Web, de criação de uma linguagem de padrões e de construção e instanciação do framework. O subprocesso de engenharia reversa utiliza sistemas presentes na Web para derivar um modelo do domínio de aplicação. O desenvolvimento da linguagem de padrões é baseado no modelo do domínio e a construção do framework utiliza essa linguagem de padrões como base de todo o processo. Os produtos resultantes do uso desse processo para o domínio dos leilões virtuais, a Linguagem de Padrões LV e o Framework Qd+, também são apresentados.; A process for the development of web-based information systems frameworks is proposed. This process comprises a reverse engineering - for web-based information systems -, a pattern language creation, and a framework instantiation subprocesses. The reverse engineering subprocess uses existing WISs to derive an application domain model. The pattern language is created from the application domain model and the framework is developed from this pattern language. The deliverables of the application of this process to the online auctions domain...

Dynamic Mechanism Design for Online Commerce

Gallien, Jérémie
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Trabalho em Andamento Formato: 330328 bytes; application/pdf
EN_US
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Motivated by electronic commerce, this paper is a mechanism design study for sellers of multiple identical items. In the market environment we consider, participants are risk neutral and time-sensitive, with the same discount factor; potential buyers have unit demand and arrive sequentially according to a renewal process; and valuations are drawn independently from the same regular distribution. From the Revelation Principle, we can restrict our attention to direct dynamic mechanisms taking a sequence of valuations and arrival epochs as a strategic input. We define two properties (discreteness and stability), and prove that under a regularity assumption on the inter-arrival time distribution, we may at no cost of generality consider only mechanisms satisfying them. This effectively reduces the mechanism input to a sequence of valuations, allowing us to formulate the problem as a dynamic program (DP). Because this DP is equivalent to a well-known infinite horizon asset-selling problem...

Optimal Bidding in Online Auctions

Bertsimas, Dimitris J.; Hawkins, Jeff; Perakis, Georgia
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 508996 bytes; application/pdf
EN_US
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Online auctions are arguably one of the most important and distinctly new applications of the internet. The predominant player in online auctions, eBay, has over 18.9 milllion users, and it was the host of over $5 billion worth of goods sold in the year 2000. Using methods from approximate dynamic programming and integer programming, we design algorithms for optimally bidding for a single item online auction, and simultaneous or overlapping multiple online auctions. We report computational evidence using data from eBay's web site from 1772 completed auctions for personal digital assistants and from 4208 completed auctions for stamp collections that show that (a) the optimal dynamic strategy outperforms simple but widely used static heuristic rules for a single auction, and (b) a new approach combining the value functions of single auctions found by dynamic programming using an integer programming framework produces high quality solutions fast and reliably.; Singapore-MIT Alliance (SMA)

Buyout prices in online auctions

Gupta, Shobhit
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 154 p.
ENG
Relevância na Pesquisa
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Buyout options allow bidders to instantly purchase at a specified price an item listed for sale through an online auction. A temporary buyout option disappears once a regular bid above the reserve price is made, while a permanent option remains available until it is exercised or the auction ends. Buyout options are widely used in online auctions and have significant economic importance: nearly half of the auctions today are listed with a buyout price and the option is exercised in nearly one fourth of them. We formulate a game-theoretic model featuring time-sensitive bidders with independent private valuations and Poisson arrivals but endogenous bidding times in order to answer the following questions: How should buyout prices be set in order to maximize the seller's discounted revenue? What are the relative benefits of using each type of buyout option? While all existing buyout options we are aware of currently rely on a static buyout price (i.e. with a constant value), what is the potential benefit associated with using instead a dynamic buyout price that varies as the auction progresses?; (cont.) For all buyout option types we exhibit a Nash equilibrium in bidder strategies, argue that this equilibrium constitutes a plausible outcome prediction...

Temporary and Permanent Buyout Prices in Online Auctions

Gupta, Shobhit; Gallien, Jérémie
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 251636 bytes; application/pdf
EN
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Increasingly used in online auctions, buyout prices allow bidders to instantly purchase the item listed. We distinguish two types: a temporary buyout option disappears if a bid above the reserve price is made; a permanent one remains throughout the auction or until it is exercised. In a model featuring time-sensitive bidders with uniform valuations and Poisson arrivals but endogenous bidding times, we focus on finding temporary and permanent buyout prices maximizing the seller's discounted revenue, and examine the relative benefit of using each type of option in various environments. We characterize equilibrium bidder strategies in both cases and then solve the problem of maximizing seller's utility by simulation. Our numerical experiments suggest that buyout options may significantly increase a seller’s revenue. Additionally, while a temporary buyout option promotes early bidding, a permanent option gives an incentive to the bidders to bid late, thus leading to concentrated bids near the end of the auction.; Singapore-MIT Alliance (SMA)

Two topics in online auctions; 2 topics in online auctions

Beil, Damian
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 158 p.; 4843975 bytes; 4843783 bytes; application/pdf; application/pdf
ENG
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This thesis studies two operations management topics in online auctions, and is divided into two parts. Motivated by the increasing use of ShopBots to scan Internet auctions, the first part of the thesis analytically examines whether or not two competing auctioneers selling the same commodity should share, or pool, some or all of their bidders. Under pooling, the bidding population is represented by three compartments: bidders dedicated to auction 1, bidders dedicated to auction 2, and pooled bidders participating in both auctions simultaneously. Under a bidder strategy shown to induce a Bayesian equilibrium, a closed form expression for the auctioneers' expected revenue under pooling is found, and pooling is recommended where it produces a greater expected revenue than no pooling (i.e., our objective is revenue maximization). Pooling is generally found to be beneficial as long as the two auctions are not too asymmetric and the underlying valuation distribution has certain concavity characteristics. Asymptotic order statistic arguments are used where explicit characterizations are intractable. The second part of the thesis considers a manufacturer who uses a reverse, or procurement, auction to determine which supplier will be awarded a contract. Each bid consists of a price and a set of non-price attributes (e.g....

Adaptive Limited-Supply Online Auctions

Hajiaghayi, Mohammad T.; Kleinberg, Robert; Parkes, David C.
Fonte: Association for Computing Machinery Publicador: Association for Computing Machinery
Tipo: Monograph or Book
EN_US
Relevância na Pesquisa
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We study a limited-supply online auction problem, in which an auctioneer has k goods to sell and bidders arrive and depart dynamically. We suppose that agent valuations are drawn independently from some unknown distribution and construct an adaptive auction that is nevertheless value- andtime-strategy proof. For the k=1 problem we have a strategyproof variant on the classic secretary problem. We present a 4-competitive (e-competitive) strategyproof online algorithm with respect to offline Vickrey for revenue (efficiency). We also show (in a model that slightly generalizes the assumption of independent valuations) that no mechanism can be better than 3/2-competitive (2-competitive) for revenue (efficiency). Our general approach considers a learning phase followed by an accepting phase, and is careful to handle incentive issues for agents that span the two phases. We extend to the k›1 case, by deriving strategyproof mechanisms which are constant-competitive for revenue and efficiency. Finally, we present some strategyproof competitive algorithms for the case in which adversary uses a distribution known to the mechanism.; Engineering and Applied Sciences

Online Auctions for Bidders with Interdependent Values

Constantin, Florin; Ito, Takayuki; Parkes, David C.
Fonte: Association for Computing Machinery Publicador: Association for Computing Machinery
Tipo: Monograph or Book
EN_US
Relevância na Pesquisa
46.35%
Interdependent values (IDV) is a valuation model allowing bidders in an auction to express their value for the item(s) to sell as a function of the other bidders' information. We investigate the incentive compatibility (IC) of single-item auctions for IDV bidders in dynamic environments. We provide a necessary and sufficient characterization for IC in this setting. We show that if bidders can misreport departure times and private signals, no reasonable auction can be IC. We present a reasonable IC auction for the case where bidders cannot misreport departures.; Engineering and Applied Sciences

Privacy-Enhanced Reputation-Feedback Methods to Reduce Feedback Extortion in Online Auctions

Goodrich, Michael T.; Kerschbaum, Florian
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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In this paper, we study methods for improving the utility and privacy of reputation scores for online auctions, such as used in eBay, so as to reduce the effectiveness of feedback extortion. The main ideas behind our techniques are to use randomization and various schemes to escrow reputations scores until appropriate external events occur. Depending on the degree of utility and privacy needed, these external techniques could depend on the number and type of reputation scores collected. Moreover, if additional privacy protection is needed, then random sampling can be used with respect reputation scores in such a way that reputation aggregates remain useful, but individual reputation scores are probabilistically hidden from users. Finally, we show that if privacy is also desired with respect to the the reputation aggregator, then we can use zero-knowledge proofs for reputation comparisons.; Comment: Longer version of a paper appearing in ACM Conference on Data and Application Security and Privacy (CODASPY) 2011

Statistical properties of online auctions

Namazi, Alireza; Schadschneider, Andreas
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/08/2006
Relevância na Pesquisa
46.49%
We characterize the statistical properties of a large number of online auctions run on eBay. Both stationary and dynamic properties, like distributions of prices, number of bids etc., as well as relations between these quantities are studied. The analysis of the data reveals surprisingly simple distributions and relations, typically of power-law form. Based on these findings we introduce a simple method to identify suspicious auctions that could be influenced by a form of fraud known as shill bidding. Furthermore the influence of bidding strategies is discussed. The results indicate that the observed behavior is related to a mixture of agents using a variety of strategies.; Comment: 9 pages, 4 figures, to be published in Int. J. Mod. Phys. C

Bidding process in online auctions and winning strategy:rate equation approach

Yang, I.; Kahng, B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/11/2005
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Online auctions have expanded rapidly over the last decade and have become a fascinating new type of business or commercial transaction in this digital era. Here we introduce a master equation for the bidding process that takes place in online auctions. We find that the number of distinct bidders who bid $k$ times, called the $k$-frequent bidder, up to the $t$-th bidding progresses as $n_k(t)\sim tk^{-2.4}$. The successfully transmitted bidding rate by the $k$-frequent bidder is obtained as $q_k(t) \sim k^{-1.4}$, independent of $t$ for large $t$. This theoretical prediction is in agreement with empirical data. These results imply that bidding at the last moment is a rational and effective strategy to win in an eBay auction.; Comment: 4 pages, 6 figures

E-loyalty networks in online auctions

Jank, Wolfgang; Yahav, Inbal
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/10/2010
Relevância na Pesquisa
46.61%
Creating a loyal customer base is one of the most important, and at the same time, most difficult tasks a company faces. Creating loyalty online (e-loyalty) is especially difficult since customers can ``switch'' to a competitor with the click of a mouse. In this paper we investigate e-loyalty in online auctions. Using a unique data set of over 30,000 auctions from one of the main consumer-to-consumer online auction houses, we propose a novel measure of e-loyalty via the associated network of transactions between bidders and sellers. Using a bipartite network of bidder and seller nodes, two nodes are linked when a bidder purchases from a seller and the number of repeat-purchases determines the strength of that link. We employ ideas from functional principal component analysis to derive, from this network, the loyalty distribution which measures the perceived loyalty of every individual seller, and associated loyalty scores which summarize this distribution in a parsimonious way. We then investigate the effect of loyalty on the outcome of an auction. In doing so, we are confronted with several statistical challenges in that standard statistical models lead to a misrepresentation of the data and a violation of the model assumptions. The reason is that loyalty networks result in an extreme clustering of the data...

A Framework for Realtime Online Auctions

Rumpe, Bernhard; Wimmel, Guido
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/09/2014
Relevância na Pesquisa
46.44%
Among the existing E-Commerce applications, online auctions are the most influential ones. Their impact on trading in the B2B (business to business) as well as in the B2C (business to consumer) and C2C (consumer to consumer) areas will be inevitable. This article describes the architecture of a web-based realtime online auction system, together with the functional and technical requirements that evolved during the development process and heavily influenced the architecture. From the point of view of this real world case study, ways to minimize the development time and yet ensure a robust and flexible system are explained: combining standard software and self- developed components, reusing code wherever possible, and employing the eXtreme Programming approach and its test concepts.; Comment: 13 pages, 4 figures

Enabling Automatic Certification of Online Auctions

Bai, Wei; Tadjouddine, Emmanuel M.; Guo, Yu
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/04/2014
Relevância na Pesquisa
46.37%
We consider the problem of building up trust in a network of online auctions by software agents. This requires agents to have a deeper understanding of auction mechanisms and be able to verify desirable properties of a given mechanism. We have shown how these mechanisms can be formalised as semantic web services in OWL-S, a good enough expressive machine-readable formalism enabling software agents, to discover, invoke, and execute a web service. We have also used abstract interpretation to translate the auction's specifications from OWL-S, based on description logic, to COQ, based on typed lambda calculus, in order to enable automatic verification of desirable properties of the auction by the software agents. For this language translation, we have discussed the syntactic transformation as well as the semantics connections between both concrete and abstract domains. This work contributes to the implementation of the vision of agent-mediated e-commerce systems.; Comment: In Proceedings FESCA 2014, arXiv:1404.0436

E-Business Experiences with Online Auctions

Rumpe, Bernhard
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/09/2014
Relevância na Pesquisa
46.61%
Online auctions are among the most influential e-business applications. Their impact on trading for businesses, as well as consumers, is both remarkable and inevitable. There have been considerable efforts in setting up market places, but, with respects to market volume, online trading is still in its early stages. This chapter discusses the benefits of the concept of Internet marketplaces, with the highest impact on pricing strategies, namely, the conduction of online business auctions. We discuss their benefits, problems and possible solutions. In addition, we sketch actions for suppliers to achieve a better strategic position in the upcoming Internet market places.; Comment: 13 pages, 5 figures

The BARISTA: A model for bid arrivals in online auctions

Shmueli, Galit; Russo, Ralph P.; Jank, Wolfgang
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/12/2007
Relevância na Pesquisa
46.61%
The arrival process of bidders and bids in online auctions is important for studying and modeling supply and demand in the online marketplace. A popular assumption in the online auction literature is that a Poisson bidder arrival process is a reasonable approximation. This approximation underlies theoretical derivations, statistical models and simulations used in field studies. However, when it comes to the bid arrivals, empirical research has shown that the process is far from Poisson, with early bidding and last-moment bids taking place. An additional feature that has been reported by various authors is an apparent self-similarity in the bid arrival process. Despite the wide evidence for the changing bidding intensities and the self-similarity, there has been no rigorous attempt at developing a model that adequately approximates bid arrivals and accounts for these features. The goal of this paper is to introduce a family of distributions that well-approximate the bid time distribution in hard-close auctions. We call this the BARISTA process (Bid ARrivals In STAges) because of its ability to generate different intensities at different stages. We describe the properties of this model, show how to simulate bid arrivals from it, and how to use it for estimation and inference. We illustrate its power and usefulness by fitting simulated and real data from eBay.com. Finally...

Agent Based Trust Management Model Based on Weight Value Model for Online Auctions

Sathiyamoorthy, E.; Iyenger, N. Ch. Sriman Narayana; Ramachandran, V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/04/2010
Relevância na Pesquisa
46.64%
This paper is aimed at the stipulations which arise in the traditional online auctions as a result of various anomalies in the reputation and trust calculation mechanism. We try to improve the scalability and efficiency of the online auctions by providing efficient trust management methodology considering several factors into consideration. A comparison between the performance of the auctions system with and without the agent methodology is done with good results; Comment: 17Pages

The Timing of Bid Placement and Extent of Multiple Bidding: An Empirical Investigation Using eBay Online Auctions

Borle, Sharad; Boatwright, Peter; Kadane, Joseph B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/09/2006
Relevância na Pesquisa
46.83%
Online auctions are fast gaining popularity in today's electronic commerce. Relative to offline auctions, there is a greater degree of multiple bidding and late bidding in online auctions, an empirical finding by some recent research. These two behaviors (multiple bidding and late bidding) are of ``strategic'' importance to online auctions and hence important to investigate. In this article we empirically measure the distribution of bid timings and the extent of multiple bidding in a large set of online auctions, using bidder experience as a mediating variable. We use data from the popular auction site \url{www.eBay.com} to investigate more than 10,000 auctions from 15 consumer product categories. We estimate the distribution of late bidding and multiple bidding, which allows us to place these product categories along a continuum of these metrics (the extent of late bidding and the extent of multiple bidding). Interestingly, the results of the analysis distinguish most of the product categories from one another with respect to these metrics, implying that product categories, after controlling for bidder experience, differ in the extent of multiple bidding and late bidding observed in them. We also find a nonmonotonic impact of bidder experience on the timing of bid placements. Experienced bidders are ``more'' active either toward the close of auction or toward the start of auction. The impact of experience on the extent of multiple bidding...

Online Auction Markets

Yao, Song
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação Formato: 1538884 bytes; application/pdf
Publicado em //2009 EN_US
Relevância na Pesquisa
36.93%

Central to the explosive growth of the Internet has been the desire

of dispersed buyers and sellers to interact readily and in a manner

hitherto impossible. Underpinning these interactions, auction

pricing mechanisms have enabled Internet transactions in novel ways.

Despite this massive growth and new medium, empirical work in

marketing and economics on auction use in Internet contexts remains

relatively nascent. Accordingly, this dissertation investigates the

role of online auctions; it is composed of three essays.

The first essay, ``Online Auction Demand,'' investigates seller and

buyer interactions via online auction websites, such as eBay. Such

auction sites are among the earliest prominent transaction sites on

the Internet (eBay started in 1995, the same year Internet Explorer

was released) and helped pave the way for e-commerce. Hence, online

auction demand is the first topic considered in my dissertation. The

second essay, ``A Dynamic Model of Sponsored Search Advertising,''

investigates sponsored search advertising auctions, a novel approach

that allocates premium advertising space to advertisers at popular

websites, such as search engines. Because sponsored search

advertising targets buyers in active purchase states...