A Difficulty in Trust Modelling

There are various trust models, and no pair are the same. Why is there no consensus on what the best trust model is yet? In this paper, we prove some impossibility results, that suggests that no perfect trust model exists. We provide a general meta-model of trust models. A new concept, belief-consistence, is introduced. If a trust model is not belief-consistent, then it cannot model anyone’s beliefs. We show that trust models without uncertainty can only be belief-consistent is an extremely simple case. Moreover, full trust models cannot be belief-consistent, even with uncertainty. Finally, we show how any discrepancies in belief can be blown up into arbitrary errors.