رویکرد مبتنی بر بازار برای مدیریت ریسک معاملات نقطه به نقطه

Market-based principles can be used to manage the risk of distributed peer-to-peer transactions. This is demonstrated by Ptrim, a system that builds a transaction default market on top of a main transaction processing system, within which peers offer to underwrite the transaction risk for a slight increase in the transaction cost. The insurance cost, determined through market-based mechanisms, is a way of identifying untrustworthy peers and perilous transactions. The risk of the transactions is contained, and at the same time members of the peer-to-peer network capitalise on their market knowledge by profiting as transaction insurers. We evaluated the approach through trials with the deployed Ptrim prototype, as well as composite experiments involving real online transaction data and real subjects participating in the transaction default market. We examine the efficacy of our approach both from a theoretical and an experimental perspective. Our findings suggest that the Ptrim market layer functions in an efficient manner, and is able to support the transaction processing system through the insurance offers it produces, thus acting as an effective means of reducing the risk of peer-to-peer transactions. In our conclusions we discuss how a system like Ptrim assimilates properties of real world markets, and its potential exposure and possible countermeasures to events such as those witnessed in the recent global financial turmoil.

It is being progressively recognised that information systems and applications supporting collaborative tasks, including online transaction processing systems, that currently follow centralized client-server models can also be based on the maturing wave of peer-to-peer architectures [53] and [3]. In order to manage and reduce the risk inherent in peer-to-peer transactions and their decentralised and uncontrolled environment, a variety of approaches have been proposed, with reputation and trust management systems being the most prominent (see Section 2.2). These aim to provide peers with estimates of the risk involved in their transactions, based on the observed past behaviour of their counterparties. Though reputation management systems (either centralized or distributed) offer a lot in this direction, the information they provide about past behaviour may not be enough to accurately assess the risk involved in a transaction. Open issues, to name but a few, include the fact that not all transactions receive feedback [49], shortcomings in the way reputation information is represented [14], perceived, and used by the transacting parties (especially for inexperienced users) [28], and dealing with participants lacking past transactions [23]. In a recent study, for instance, it was suggested that the way in which the positive and negative feedback is presented to users of the eBay system can make it difficult for buyers to evaluate past illegal behaviour of sellers [29]. As a result, there still is considerable concern over the amount of risk involved in online transactions, even with the support of reputation management systems [21], [15] and [25]. In this work we propose a novel approach, based on the principles and instruments used in different (including commercial and financial) markets for managing, transferring or reducing credit and transaction risk. We demonstrate the practicality of this approach and evaluate its efficacy through the prototype Ptrim (“peer-to-peer transaction risk management”) system. On top of a generic transaction processing system, Ptrim creates a peer-to-peer transaction insurance market-like layer that is used to manage the risk of transaction default. The transacting peers have the option to request offers from peers in this layer to underwrite the risk of their transaction, and therefore alleviate themselves from the need to collect, process and evaluate reputation information. A transaction default market is thus built on top of the main transaction processing system, within which the cost of “insuring” a transaction is determined through market-based mechanisms. The main contribution of our approach is that it proposes a novel way of identifying untrustworthy peers and perilous transactions, based on the insurance offers the market will produce; the risk of peer-to-peer transactions is contained at a small additional cost; and at the same time, our system showcases a way for members of a peer-to-peer network to participate in a new profitable role, as transaction insurers. It should be noted that although we implement and examine our proposed approach within a peer-to-peer environment, its underlying principles could also apply to different, not completely decentralised network architectures. In this paper, we first present the key concepts of market-based transaction risk management that our approach is based on, briefly touching on the underlying economics principles, and we examine its relation to other work (see Section 2). We proceed to present the design, architecture and implementation of our proposed system in Section 3, and our methodology for testing and evaluating it both theoretically and practically (see Section 4), which includes studies with a deployed prototype, as well as experiments involving both real subjects and real transaction data crawled from the eBay online auction site. We discuss our evaluation results and outcomes in Section 5, and our system’s current limitations and planned future work in Section 6.

Our approach for managing the risk of distributed peer-to-peer transactions is based on the principles governing financial markets. Ptrim builds and utilises a transaction default market on top of a main transaction processing system, within which peers offer to underwrite the transaction risk for a slight increase in the transaction cost. The cost is determined through market-based mechanisms, and forms a way of identifying untrustworthy peers and perilous transactions. The risk of the transactions is effectively minimised while the transacting peers are alleviated from the need to collect, process and evaluate reputation information. At the same time our system showcases a way for members of a peer-to-peer network to capitalise on their market knowledge by participating in a new role, as transaction insurers. The Ptrim approach can be considered as an alternative, but also as complementary to the use of distributed reputation management systems. We evaluated and discussed the performance of our approach through a methodology relevant to the one used for distributed reputation management systems. Our experimental findings suggest that our system functions in an efficient manner, and is able to support the transaction processing layer through the insurance offers it produces. At the same time our findings expose interesting observations regarding the behaviour of the subjects of our trials, and how this behaviour affects the market and its growth towards maturity. We discussed the system’s current limitations and planned future work. One additional concept we feel might be worth exploring concerns the fundamental “tension” between a centrally managed trust system, and the decentralized market-based approach we advocate. How does a system like eBay, for instance, reflect the value of the reputation management services they offer in its cost model, and how can one relate this to our market-based approach from a financial perspective? In theory, is our approach going to be cheaper or more expensive for the participants? This is an interesting open issue beyond the scope of the current work that we feel warrants some more in-depth analysis. In the meantime, we believe that this work may provide an incentive for other researchers to utilise our concepts in different applications and cases.