From Subjective Trust to Objective Trustworthiness in On-line Social Networks: Overview and Challenges

Nowadays dozens of people share their content in the current Web 2.0 space, talk with friends in social networking sites such as Facebook and live on the Net in many other ways. They do all this quite naturally, forgetting the healthy cautiousness sometimes. In real life we rely on trusted people. Do we know how to reflect real-world trust mechanisms into on-line social software? In the article we focused to bring overview on state of the art in main ideas behind a trust processing in online social networking systems. What are common sources of subjective trust, how the trust emerges and what are the sources of trust dynamics? How can be trust captured into the systems, how can be explicit trust processed to infer indirect trust, the trust between users who do not know each other? And what are the ways to infer objective metrics of trust, the reputation or trustworthiness? Finally, we point out selected challenges related to the trust in current highly dynamic social networks.