P. Michael Melliar-Smith

Toward Trustworthy Coordination of Web Services Business Activities

We present a lightweight Byzantine fault tolerance (BFT) algorithm, which can be used to render the coordination of web services business activities (WS-BA) more trustworthy. The lightweight design of the BFT algorithm is the result of a comprehensive study of the threats to the WS-BA coordination services and a careful analysis of the state model of WS-BA. The lightweight BFT algorithm uses source ordering, rather than total ordering, of incoming requests to achieve Byzantine fault tolerant, state-machine replication of the WS-BA coordination services. We have implemented the lightweight BFT algorithm, and incorporated it into the open-source Kandula framework, which implements the WS-BA specification with the WS-BA-I extension. Performance evaluation results obtained from the prototype implementation confirm the efficiency and effectiveness of our lightweight BFT algorithm, compared to traditional BFT techniques.

Dynamic Pricing for Time-Limited Goods in a Supplier-Driven Electronic Marketplace

Existing e-commerce systems employ a pull model of marketing where buyers, possibly through agents, search the e-market for suppliers offering the product of their choice. In contrast, the push model where suppliers’ agents approach buyers with their products, has been relatively less investigated. Push strategies are particularly appropriate for commodities that have a short shelf-life and, therefore, an elastic demand curve, allowing suppliers to exploit unexpected supply. The speed and low cost of e-commerce makes it particularly suited to the push paradigm. In this paper, we consider time-limited goods in a supplier driven marketplace that employs the push model of marketing. When constrained by a strict deadline to sell the good, the supplier uses a mobile sales agent that visits every buyer and estimates the short run demand curve of the good. At every buyer, the sales agent also employs a heuristic technique called the Maximum Returns Algorithm to recalculate the price of the good, so that the supplier can obtain the best possible gross returns from trading with the buyers. On the other hand, when the deadline to sell is not stringent, the sales agent negotiates the exchange at a point that improves both the buyer’s utility and the supplier’s profit, as compared to the exchange point without negotiation.

Maximizing Welfare Through Cooperative Negotiation In A Multi-Agent Internet Economy

E-commerce over the Internet has become an attractive means of conducting business in todays world. However, the principles of classical economics demand a fresh insight before they can be adapted to the market structure presented by the Internet. Here, we investigate markets for goods that are characterized by an experience-limited supply curve. We propose an algorithm that maximizes the welfare in the e-market by maximizing the combined profit of the buyers and sellers. For this, the buyers and sellers must reveal their value and cost curves to a trusted intermediary who can determine the transaction that maximizes their joint welfare. We show that accurate revelation of hidden profits offers better incentives, both to the buyers and the sellers, than inaccurate or incomplete revelation.

Protecting the iTrust Information Retrieval Network against Malicious Attacks

This paper presents novel statistical algorithms for protecting the iTrust information retrieval network against malicious attacks. In iTrust, metadata describing documents, and requests containing keywords, are randomly distributed to multiple participating nodes. The nodes that receive the requests try to match the keywords in the requests with the metadata they hold. If a node finds a match, the matching node returns the URL of the associated information to the requesting node. The requesting node then uses the URL to retrieve the information from the source node. The novel detection algorithm determines empirically the probabilities of the specific number of matches based on the number of responses that the requesting node receives. It also calculates the analytical probabilities of the specific numbers of matches. It compares the observed and the analytical probabilities to estimate the proportion of subverted or non-operational nodes in the iTrust network using a window-based method and the chi-squared statistic. If the detection algorithm determines that some of the nodes in the iTrust network are subverted or non-operational, then the novel defensive adaptation algorithm increases the number of nodes to which the requests are distributed to maintain the same probability of a match when some of the nodes are subverted or non-operational as compared to when all of the nodes are operational. Experimental results substantiate the effectiveness of the detection and defensive adaptation algorithms for protecting the iTrust information retrieval network against malicious attacks.

Peer-to-peer publication, search and retrieval using the Android mobile platform

Abstract In this paper, we present the iTrust over Wi-Fi Direct system, which is a peer-to-peer publication, search and retrieval system for mobile ad hoc networks. We describe the iTrust over Wi-Fi Direct architecture and components, as implemented on the Android platform for mobile devices, and show how user applications can easily interface with iTrust over Wi-Fi Direct. We also describe the iTrust over Wi-Fi Direct networking model, and the interactions with the Android and Linux stacks. In addition, we describe the peer management protocol for iTrust over Wi-Fi Direct on the Android platform, which enables peers to construct a mobile ad hoc network by automatically discovering and connecting peers. We discuss deficiencies of the Android platform for Wi-Fi Direct, and present our solution to address those limitations. Finally, we present a performance evaluation of iTrust over Wi-Fi Direct in terms of the match probabilities without and with message forwarding, the peer management overhead, and the resource transfer latency.