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A Reputation-Based Model for Trust Evaluation in Social Cyber-Physical Systems

The concept of social networking is integrated into the Cyber-Physical Systems (CPSs) for the purpose of allowing smart objects to establish social relationships in an autonomous way. Solutions based on social relationships are considered to be promising approaches for resource/service discovery. The primary issues in a social-CPS (SCPS) involve how to define, quantify and eventually establish social relationships between objects, and how to build a reliable system. In this paper, we first put forward a definition of the trustworthiness management in a SCPS. And we subsequently build a reputation-based trust mechanism that quantifies the direct trustworthiness between objects, using a fuzzy logic model to address the perceptions of uncertainty and risk contained in this concept of trust. Then we propose a light-weight paradigm for service discovery which makes use of indirect trustworthiness for service provider ranking, based on the theories of the directed acyclic graph. Several rules are introduced for the weighted recommendation paths, and an expurgation mechanism is proposed to simplify the process of indirect trustworthiness evaluation. The convincing experimental results show that our mechanism performs better than the other two methods with four aspects of satisfaction rate, quality of recommended information, accuracy of trust assessment and convergence time.