Social media greatly enables people to participate in online activities and shatters the
barrier for online users to create and share information at any place at any time. However the
explosion of user-generated content poses novel challenges for online users to find relevant
information or in other words exacerbates the information overload problem. On the other
hand the quality of user-generated content can vary dramatically from excellence to abuse or
spam resulting in a problem of information credibility. The study and understanding of trust
can lead to an effective approach to addressing both information overload and credibility
problems. Trust refers to a relationship between a trustor (the subject that trusts a target
entity) and a trustee (the entity that is trusted). In the context of social media trust
provides evidence about with whom we can trust to share information and from whom we can accept
information without additional verification. With trust we make the mental shortcut by
directly seeking information from trustees or trusted entities which serves a two-fold
purpose: without being overwhelmed by excessive information (i.e. mitigated information
overload) and with credible information due to the trust placed on the information provider
(i.e. increased information credibility). Therefore trust is crucial in helping social media
users collect relevant and reliable information and trust in social media is a research topic
of increasing importance and of practical significance. This book takes a computational
perspective to offer an overview of characteristics and elements of trust and illuminate a wide
range of computational tasks of trust. It introduces basic concepts deliberates challenges and
opportunities reviews state-of-the-art algorithms and elaborates effective evaluation methods
in the trust study. In particular we illustrate properties and representation models of trust
elucidate trust prediction with representative algorithms and demonstrate real-world
applications where trust is explicitly used. As a new dimension of the trust study we discuss
the concept of distrust and its roles in trust computing.
