## 4 Iterative Trust and Reputation Computation Model
### Reputation System in B2C E-Commerce  
Trust in a service-oriented network environment is the subjective psychological status of the service clients or buyers, and relies on the promise made by online service providers. The aim of developing trust is to reduce transaction risks and uncertainties. Reputation systems collect, process, and aggregate trustworthy information regarding participants or services which help future users make optimal decisions. The role of trust is to nurture and sustain reputations, which is essentially a trust-building process. In network environments, service providers earn and retain trust via reputations. Without trust, a good reputation will erode. As a child is the father of a man, trust begets reputation. Loss of trust can damage a reputation. Reputation is a close relative of trust, yet they are not the same. Therefore, while a reputation may be trustworthy, it generally consists of a whole range of characteristics other than trust. Online service providers can develop and sustain reliable reputations via the processes of building trust.  
There are two types of reputation system architectures in service-oriented network environments in which different trust ratings are gathered and stored [52]. These are referred to as centralized and distributed architectures. In centralized reputation architectures, the management of trust and reputation in network environments is based on centralized trust databases. Further, trust information regarding the performance of participants is collected, stored, and computed by a third central reputation authority. Reputation rankings and scores are available publicly, and service clients and users can consult with these for their next round of transactions. Such reputation systems include taobao, dangdang, and 360 buy. Distributed reputation systems have no central reputation authority to submit their reputation ratings. Each client collects ratings from other participants, and each client records their opinion regarding their transactions with the service providers. When a client desires knowledge of the reputation of a potential transaction partner or service provider, he or she needs to obtain ratings from other clients who have already completed transactions with the same service provider and thus calculate the reputation status based on the score ratings. Such reputation systems are reputation architectures in C2C e-commerce and P2P networks. Reputation system architecture can also be classified as bidirectional or unidirectional [53]. In bidirectional architecture, all users can be both service providers and service clients. In the case of unidirectional architecture, service providers and their products are rated by service clients. The proposed reputation system for B2C e-commerce based on the relationship of trust and reputation is centralized and is unidirectional in terms of its architecture, which can be illustrated in Figure 1. The trust status and reviews of the service provider provided by the service clients are collected, stored, and computed by a third central authority. Further, reputation computation results are performed by the values of trust reviews, which can be consulted within the next round of transactions.