On the Use of Causal Rules to Specify How Trust Impacts Change in Knowledge and Belief

Abstract

We are concerned with models of trust, and the way that trust impacts changes in knowledge and belief. In order to address this problem, we consider transformations on Kripke structures in modal logic. We start with simple trust rules that specify how reported information impacts the truth of a modal formula. Trust rules are defined with respect to a particular source. So an individual trust rule basically indicates when a source’s reported information will cause the truth value of a modal formula to change. In the context of epistemic logic, this means that a trust rule indicates when a report will affect the knowledge or belief of the recipient. We demonstrate how a set of trust rules defines a model transformation in which the underlying accessibility relation is modified to ensure all rules are satisfied. This transformation captures how much the underlying source is trusted to impact the recipients perspective on the world. Model transformations of this kind are commonly used to capture belief change in Dynamic Epistemic Logic. What is distinct in our approach is that we show how simple rules can give a compact and flexible specification of trust in an information source. Our approach is also general, in the sense that we consider arbitrary modal change, which means we can capture different conceptions of knowledge and belief. We compare our approach with related work, particularly on the formaliziation of sensing actions. Future directions and applications are also considered.