Peer-to-peer (P2P) systems represent nowadays a large portion of Internet traffic, and are fundamental data sources. In a pure P2P system, since no peer has the power or responsibility to monitor and restrain others behaviours, there is no method to verify the trustworthiness of shared resources, and malicious peers can spread untrustworthy data objects to the system. Furthermore, data descriptions are often simple features directly connected to data or annotations based on heterogeneous schemas, a fact that makes difficult to obtain a single coherent trust value on a resource. This chapter describes techniques where the combination of Semantic Web and peer-to-peer technologies is used for expressing the knowledge shared by peers in a well-defined and formal way. Finally, dealing with Semantic-based P2P networks, the chapter suggests a research effort in this direction, where the association between cluster-based overlay networks and reputation systems based on numerical approaches seems to be promising.
TopTrust And Reputation Systems: An Overview
The increasingly electronic commerce transactions, Web-based access to information, interpersonal interactions via electronic means, have led to a growing interest and study about trustworthiness of these services, since it is often hard to assess the trustworthiness of remote entities. In particular what is difficult is to collect evidence about unknown transaction partners, and that makes it hard to distinguish between high and low quality service providers in a computer network.
Trust is not a new research topic in computer science, and depending on the area where the concept of trust is used--security and access control in computer networks, reliability in distributed systems, game theory and agent systems, and policies for decision making under uncertainty--it varies in these different communities in how it is represented, computed, and used.
In this section, according in particular to (Jösang, Ismail, & Boyd, 2007) (Artz & Gil, 2007) (Ramchurn, Huynh, & Jennings, 2004) (Grandison & Sloman, 2000) we will give an overview of trust research in computer science, describing how different areas define and use trust in a variety of contexts. The various definitions of trust will be reviewed and classified, with particular reference to collaborative sanctioning systems, known as reputation systems.