Computing price trajectories in combinatorial auctions with proxy bidding

Proxy bidding has proven useful in a variety of real auction formats – most notably eBay – and has been proposed for the nascent field of combinatorial auctions. Previous work on proxy bidding in combinatorial auctions requires the auctioneer to run the auction with myopic bidders to determine the outcome. In this paper, we present a radically different approach that computes the bidders’ allocation of their attention across the bundles only at “inflection points”. Inflections are caused by the introduction of a new bundle into an agent’s demand set, a change in the set of currently competitive allocations, or the withdrawal of an agent from the set of active bidders. This approach has several advantages over alternatives, including that it computes exact solutions and is invariant to the magnitude of the bids.     

Bidding agents for online auctions with hidden bids

There is much active research into the design of automated bidding agents, particularly for environments that involve multiple decoupled auctions. These settings are complex partly because an agent’s strategy depends on information about other bidders’interests. When bidders’ valuation distributions are not known ex ante, machine learning techniques can be used to approximate them from historical data. It is a characteristic feature of auctions, however, that information about some bidders’valuations is systematically concealed. This occurs in the sense that some bidders may fail to bid at all because the asking price exceeds their valuations, and also in the sense that a high bidder may not be compelled to reveal her valuation. Ignoring these “hidden bids” can introduce bias into the estimation of valuation distributions. To overcome this problem, we propose an EM-based algorithm. We validate the algorithm experimentally using agents that react to their environments both decision-theoretically and game-theoretically, using both synthetic and real-world (eBay) datasets. We show that our approach estimates bidders’ valuation distributions and the distribution over the true number of bidders significantly more accurately than more straightforward density estimation techniques. Editors: Amy Greenwald and Michael Littman An earlier version of this work was presented at the Workshop on Game-Theoretic and Decision-Theoretic Agents (GTDT) 2005, Edinburgh, Scotland.     

Reactivity based model to study online auctions dynamics

Online auctions have challenged many assumptions and results from the traditional economic auction theory. Observed bidder behavior in online auctions often deviates from equilibrium strategies postulated by economic theory. In this research, we consider an online auction as an information system that provides a long-duration, information-rich, dynamic application environment in which users (bidders) interact with the system in a feedback loop, in what we term reactivity. Bidders react to the observed conditions of the auction and events triggered by actions of other bidders. In this work we propose a new characterization model with the purpose of isolating the segments of the auction in which users react to the auction conditions and events. Through this model, it is possible to enrich the auction characterization. Despite the existence of other bidding characterization models, none of them is enough for understanding the factors that characterize and explain the auction dynamics. We present results which demonstrate the advantages of applying our methodology. The final objective is to gain an understanding of what drives the dynamics of online auctions, the role of reactivity in the auction dynamics, and how the outcome of the auction is affected by the particular dynamics of the system.

基于Proxy的网络计费方法

本文主要论述代理服务器的用途及工作原理,并结合某学院校园网接入 Ｉｎｔｅｒｎｅｔ的 网络方案,详细阐述了基于ＭＳ Ｐｒｏｘｙ Ｓｅｒｖｅｒ的网络计费方案和实现方法。     

WWW代理服务器的研究与实现

代理服务器是缓解安全总理２的有效方法之一。在对ｈｔｔｐ协议分析的基础上,描述了ＷＷＷ代理服务器的工作流程和实现原理,并据此开发了一个可供衫的ＷＷＷ代理服务器。     

Real-time detection of shill bidding in online auctions: A literature review

Online auctions have become an increasingly popular and convenient way for conducting ecommerce transactions on the Web. However, the rapid surge of users participating in online auctions has led to auction fraud. Among the types of auction fraud, the most prominent is Shill bidding. Shill bidding is intentionally fake bidding by a seller on his/her own auction to inflate the final price. This can be accomplished either by the seller himself/herself or by someone colluding with the seller to place fake bids on his/her behalf. Therefore, it is difficult to manually investigate the large amount of auctions and bidders for shill bidding activities. Detecting shill bidding in real-time is the most effective way to reduce the loss result of the auction fraud. Researchers have proposed multiple approaches and experimented to control the losses incurred due to shill bidding. This paper investigates the real-time detection techniques of shill bidding. It also provides a brief overview of major work that has been conducted in shill bidding detection including both offline and real-time approaches. Furthermore, this paper identifies research gaps in the detection and prevention of shill bidding behaviours. It also provides future research issues and challenges to detect shill bidding in real-time.     

网络代理服务器的设计与实现

随着计算机网络技术的广泛应用,企业内部网络发展得非常迅速。防火墙作为一种网络安全技术的重要方法,有效地保护了企业内部网络的安全。该文主要对网络代理服务器进行了设计与研究,首先阐述了防火墙的功能,接着分析了代理服务器的工作原理,详细描述了执行流程,最后介绍了基于VB环境下,代理服务器的设计与实现方法。     

移动警务系统中一种代理服务器的设计与实现

根据移动警务自身的特点和发展趋势,结合移动警务的总体结构,阐述了代理服务器(proxy)的功能与特点,详细介绍了代理服务器中线程池的管理及具体实现,提高了代理服务器的工作效率,实现了对警务系统的有力增强。     

基于SOCKSv5代理的ESMTP设计与实现

本文对基于SOCKSv5代理的邮件发送程序进行了深入而详细的探讨。文中首先对SOCKSv5协议和ESMTP协议的原理及过程进行了深入的分析,并在分析的基础上得出了基于SOCKSv5代理邮件发送程序的一般流程图,最后给出了程序实现部分关键代码。     

一种具有双重性质的盲代理签名

提出了一种新的盲代理多重签名方案，该方案把盲代理签名和代理多重签名结合在一起，使其具有双重性质。     

代理服务器在Internet/Intranet中的应用

以微软公司代理服务器软件ＭＳＰｒｏｘｙ Ｓｅｒｖｅｒ２．０为例,详细阐述了代理服务器的功能、设计、安装及使用。     

The influence of equivocality in purchasing tasks on the selection of transaction channels in online auctions

Online auctions are one of the most active business models used in electronic commerce. Previous researchers address issues of online auction behaviour focusing on the factors influencing bidding intentions, but how bidders choose transaction channels to complete the consumption process is not examined before. This study conducts an experiment to manipulate the equivocality of purchasing task. Results show that when purchasing a product with higher task equivocality, bidders tend to choose a communication channel with higher information richness, and select a payment and product delivery channel with lower risk. When purchasing a product with lower task equivocality, bidders tend to select a communication channel with lower information richness, and tolerate higher risk to complete the payment and product delivery process.     

防火墙逆向代理的设计与实现

网络地址翻译（ＮＡＴ）是防火墙的主要技术之一。传统的ＮＡＴ有不能对外提供服务,协议不透明,不易扩展应用等缺点。逆向代理技术较好地解决了这些问题,能实现双向的地址映射和虚拟专用网,并运用ＨＡＳＨ检索接收从外网到内网的逆向连接,实现与应用的兼容。     

代理盲签名方案的安全性分析

代理签名是指原始签名人将签名权力委托给代理签名人,由代理签名人代表原始签名人对消息进行签名。盲签名是指签名人不知道所签消息的具体内容。Zhao和Liu结合代理签名和盲签名的特性提出了一种代理盲签名,该文指出Zhao和Liu提出的代理盲签名方案存在广泛的伪造攻击、原始签名人的伪造攻击和消息拥有者的伪造攻击等安全缺陷,并提出了改进的方案,改进后的方案可以有效地避免原始签名人和消息拥有者的伪造攻击。     

基于嵌入式Linux的下载代理服务器的设计与实现

本文提出了一种具有下载、代理功能的小型网络服务器的设计方案,以及开发环境和运行环境。该模型以三星公司S3C2440芯片为核心,设计实现了包含以太网接口、USB端口的嵌入式硬件设备平台,在此平台上移植嵌入式Linux操作系统,并根据软硬件特性移植相应的应用程序,从而实现了具有下载、代理功能的小型网络服务器。     

一种基于SSL/TLS的Web安全代理的设计与实现

SSL Web代理能有效保护Internet上数据传输和存有敏感信息的Web服务器的安全。但是SSL协议中大量的数据处理带来的性能瓶颈和协议实现中受到的安全威胁将严重影响SSL Web代理的效用。该文在分析SSL／TLS协议性能和安全的基础上,设计并实现了一种高效的、安全的SSL／TLS Web代理。     

基于线程池技术WWW代理服务器的设计与实现

首先描述了WWW代理服务器的工作流程和实现原理;然后在分析已有的线程池模型的基础上提出了一个新的模型,该模型能进一步地降低代理服务器的运行开销,加快对客户请求的响应速度;最后给出了基于此模型的代理服务器的实现方案。     

Multi-attribute auctions with different types of attributes: Enacting properties in multi-attribute auctions

Multi-attribute auctions allow agents to sell and purchase goods and services taking into account more attributes than just price (e.g. service time, tolerances, qualities, etc.). In this paper we analyze attributes involved during the auction process and propose to classify them between verifiable attributes, unverifiable attributes and auctioneer provided attributes. According to this classification we present VMA2, a new Vickrey-based reverse multi-attribute auction mechanism, which takes into account the different types of attributes involved in the auction and allows the auction customization in order to suit the auctioneer needs. On the one hand, the use of auctioneer provided attributes enables the inclusion of different auction concepts, such as social welfare, trust or robustness whilst, on the other hand, the use of verifiable attributes guarantee truthful bidding. The paper exemplifies the behavior of VMA2 describing how an egalitarian allocation can be achieved. The mechanism is then tested in a simulated manufacturing environment and compared with other existing auction allocation methods.     

具备高速缓存的HTTP代理防火墙的设计与实现

HTTP代理防火墙是保障网络倍息安全的重要手段，但其实现方式会影响网络通信效率，高速缓存是解决这一问题的可行方法。文章根据一个已实现的实例，讨论了具备高速缓存的HTTP代理防火墙的工作过程、实现原理以及缓存机制。