A Dempster-Shafer theory based witness trustworthiness model to cope with unfair ratings in e-marketplace

Reputation systems have contributed much to resisting against the threats from malicious seller agents in electronic marketplaces. Buyer agents can benefit from modeling the reputation of seller agents to make a decision on which seller to have transaction with. However, the existence of unfair ratings decreases the accuracy of the seller agents' reputation evaluation, which will lead to inappropriate sellers to be selected and hence harm buyers' profits. In this paper, to address the problem of unfair ratings, we propose a witness trustworthiness model based on Dempster-Shafer theory to evaluate the trustworthiness of a witness's ratings regarding a particular seller. The proposed approach uses local and global ratings together to model a witness's trustworthiness which is specific for different sellers. The experimental results demonstrate that the proposed approach can effectively address the problem of unfair ratings and outperform the comparative approaches, especially when collusion attacks exist.