Exploring Different Types of Trust Propagation

Trust propagation is the principle by which new trust relationships can be derived from pre-existing trust relationship. Trust transitivity is the most explicit form of trust propagation, meaning for example that if Alice trusts Bob, and Bob trusts Claire, then by transitivity, Alice will also trust Claire. This assumes that Bob recommends Claire to Alice. Trust fusion is also an important element in trust propagation, meaning that Alice can combine Bob’s recommendation with her own personal experience in dealing with Claire, or with other recommendations about Claire, in order to derive a more reliable measure of trust in Claire. These simple principles, which are essential for human interaction in business and everyday life, manifests itself in many different forms. This paper investigates possible formal models that can be implemented using belief reasoning based on subjective logic. With good formal models, the principles of trust propagation can be ported to online communities of people, organisations and software agents, with the purpose of enhancing the quality of those communities.