Toramatsu Shintani

A volume discount-based allocation mechanism in group buying

Volume discount is seen as an effective form of electronic commerce and a promising field for applying agent technologies. In current volume discount mechanisms, items are not allocated efficiently to buyers. Namely, social surplus is not maximum in existing volume discount schemes. To solve this problem, we propose a volume discount mechanism based on the sellers reservation price and the payment adjustment value. First, a seller registers his/her items with the evaluation value functions. The sellers evaluation value is sealed and each buyer bids his/her evaluation value as sealed bid. After the deadline, the mechanism determines the allocation of bundles of items. A tentative price is decided and the payment adjustment value is calculated. Finally, the payment amount is calculated. Our mechanism has some key advantages. First, the mechanism is Pareto efficient. Second, our mechanism is a strategy-proof mechanism, that is, it has the incentive compatibility. Third, our mechanism provides individual rationality. Fourth, our mechanism is made based on the volume discount system, where the seller can give a signal indicating a discount for buyers. Finally, our mechanism weakens the influence of false name bids.

A paper recommendation mechanism for the research support system Papits

We have developed Papits, a research support system, that shares research information, such as PDF files of research papers, in computers on networks and classifies the information into research types. Papits users can share various research information and survey the corpora of their particular fields. To develop Papits, we need to design a mechanism to identify a users interest. Also, when constructing an effective paper recommendation system, it is important to carefully create users models. We propose a method to construct users models using the scale-free network. The scale-free network has vertices and edges, and ensures growth by preference attachments. Our method applies a paper viewing history to construct a scale-free network based on the word co-occurrence. A constructed network consists of vertices that represent words, and edges that represent the word co-occurrence. In our method, a paper is added to the network as indicated by a users paper viewing history. Additionally we define the topic weight. By using two elements; the topic frequency and the topic recency, we calculate the topic weight. By using the word co-occurrence in a database, we measure the topic frequency. Also, by using the Jaccard coefficient, we measure the topic recency. Our result indicates that our method can effectively recommend documents for Papits users.

A robust combinatorial auction mechanism against shill bidders

This paper presents a method for discovering and detecting shill bids in combinatorial auctions. The Vickrey-Clarke-Groves Mechanism is one of the most important combinatorial auctions because it can satisfy the strategy-proof property, individual rationality, and Pareto efficiency, that is, it is the only mechanism that simultaneously satisfies these properties. As Yokoo et al. pointed out, false-name bids and shill bids pose an emerging problem for auctions, since on the Internet it is easy to establish different e-mail addresses and accounts for auction sites. Yokoo et al. proved that VCG cannot satisfy the false-name-proof property, and they also proved that no auction protocol can satisfy all three of the above properties and the false-name proof property simultaneously. Their approach concentrates on designing a new mechanism that has desirable properties, but this is quite complicated. As a new approach against shill-bids, in this paper, we design a mechanism that utilizes VCG and an algorithm for finding potential shill bids. Our mechanism is quite simple compared with Yokoos approaches [11][12][13]. Our mechanism can judge whether there might be a shill bid from the results of the VCG procedure. We prove a theorem stating that shill bidders cannot increase their utilities unless all shill bidders win in the auction. Based on this theorem, our proposed mechanism compares the agents utilities in a conventional auction with those in an auction where a shill bidder does not join in the auction. When these agents utilities are different between the above cases, such agents might be shill bidders. Then, our mechanism allocates items to the shill bidders as a group from the set of items obtained through successful bids by the agent in the conventional auction. This process prevents shill bidders from increasing unfair profits. Furthermore, even though shill bidders participate in the auction, the sellers profit does not decrease using our proposed method. Thus, our mechanism detects shill bids when it only detects the possibility of shill bids. Our proposed method has the following three key advantages. First, we propose a method to detect shill bidders by comparison between bidders utilities. Our method is superior than existing complex mechanisms in the point of view of generalization and wide-use, because our auction mechanism employs only VCG. Second, even though there are shill bidders in an auction, incentive compatibility property is preserved using our mechanism. Finally, the schemer, in our mechanism, does never have incentive to make shill bidders. The schemers utility does not increase in our mechanism even though a schemer make shill bidders. Namely, not to make shill bidders is dominant strategy for the schemer.

MiNet: Building Ad-Hoc Peer-to-Peer Networks for Information Sharing Based on Mobile Agents

The Internet is a very popular for information sharing technology since users can share information in organizations and communities. In this paper, we present a flexible peer-to-peer networking technology for information sharing on the Internet called MiNet. In some certain communities, MiNet can construct an ad-hoc network for information sharing. MiNet enables users to share information based on mobile agents, which are implemented in a mobile agent framework MiLog. MiNet can construct ad-hoc peer-to-peer networks by encapsulating information and sending it as mobile agents that can migrate in MiNet beyond firewalls, proxies, and NATs in LANs. Therefore, MiNet can construct VPNs, which consist of several LANs covered by firewalls, etc. MiNet agents can automatically choose a destination platform according to its policies. We show the document sharing system MiDoc as an application based on MiNet. Since MiDoc is implemented using MiNet, MiDoc users can share any document among any LANs.

MiSpider: a continuous agent on web pages

In this paper, we propose a Web based agent system called MiSpider, which provides intelligent web services on web browsers. MiSpider enables users to use agents on existing browsers. Users can use MiSpider all over the world only to access the Internet. MiSpider Agent has persistency, and agents condition doesnt change if users change a browsing page. Moreover, agents have a message passing skill to communicate among the agents.

A Dynamic Rearrangement Mechanism of Web Page Layouts Using Web Agents

This paper describes a dynamic rearrangement mechanism of Web page layouts. The aim of this research is to provide webmasters or administrators with a means of determining easily the best suited content layout of their Web pages in a short period of time by automatically testing and relocating the contents with a trend of user actions. We will become able to modify dynamically the structure and layout of Web pages on the client browsers using the information of user behaviors. Our method provides the means of changing the contents inside or between Web pages and updating the contents on Web browsers, and it shorten the period of time for optimization.

A nurse scheduling system based on dynamic constraint satisfaction problem

In this paper, we describe a new nurse scheduling system based on the framework of Constraint Satisfaction Problem (CSP). In the system, we must deal with dynamic changes to scheduling problem and with constraints that have different levels of importance. We describe the dynamic scheduling problem as a Dynamic Weighted Maximal CSP (DW-MaxCSP) in which constraints can be changed dynamically. It is usually undesirable to drastically modify the previous schedule in the re-scheduling process. A new schedule should be as close to as possible to the previous one. To obtain stable solutions, we propose methodology for keeping similarity to the previous schedule by using provisional constraints that explicitly penalize changes from the previous schedule. We have confirmed the efficacy of our system experimentally.

Realizing a News Value Markup Language for News Management Systems Using NewsML

In recent years, the standardization of news management and transmission format has advanced, and NewsML (news markup language) has appeared. NewsML is a format which was decided by the IPTC (International Press Telecommunications Council). In this paper, we propose a next generation news management system based on an environment in which news management, transmission, and editing are performed. Concerning news management and transmission, our proposal, NVML (news value markup language), is a metadata description language for NewsML transmission that is to be independent of NewsML. NVML is used for two purposes. One is a metadata management for link management and distribution of NewsML documents. The other is metadata management for assigning values to news. By making link management and content management separate, both news distributors and subscribers can manage NewsML and NVML, while maintaining link adjustments. Moreover, by attaching values to news, users can search, view, and reuse news based on values. Concerning news editing, we created an input candidate support system based on news continuity and an automatic system of judging news categories.

A new approach to detecting shill bids in e-auctions

False-name bids and shill bids pose an emerging problem for auctions. To solve the problem, we propose a new method for finding shill bid in order to avoid them. Our algorithm can judge whether there might be a shill bid from the results of the bidding procedure. Further, in this paper, we propose an improved method, which can dramatically reduce the computational cost. The results demonstrate that the proposed method successfully reduces the computational cost needed to find shill bids. The contribution of our work is in the integration of the theory and detecting fraud in combinatorial auctions.

A feature selection for text categorization on research support system papits

We have developed a research support system, called Papits, that shares research information, such as PDF files of research papers, in computers on the network and classifies the information into types of research fields. Users of Papits can share various research information and survey the corpora of their particular fields of research. In order to realize Papits, we need to design a mechanism for identifying what words are best suited to classify documents in predefined classes. Further we have to consider classification in cases where we must classify documents into multivalued fields and where there is insufficient data for classification. In this paper, we present an implementation method of automatic classification based on a text classification technique for Papits. We also propose a new method for using feature selection to classify documents that are represented by a bag-of-words into a multivalued category. Our method transforms the multivalued category into a binary category to easily identify the characteristic words to classify category in a few training data. Our experimental result indicates that our method can effectively classify documents in Papits.