Goal generation from possibilistic beliefs based on trust and distrust

The extent to which a rational agent changes its beliefs may depend on several factors like the trustworthiness of the source of new information, the agent's competence in judging the truth of new information, the mental spirit of the agent (optimistic, pessimistic, pragmatic, etc), the agent's attitude towards information coming from unknown sources, or sources the agent knows as being malicious, or sources the agent knows as providers of usually correct information, and so on. We propose and discuss three different agent's belief behaviors to be used in a goal (desire) generation and adoption framework. The originality of the proposals is that the trustworthiness of a source depends not only on the degree of trust but also on an independent degree of distrust. Explicitly taking distrust into account allows us to mark a clear difference between the distinct notions of negative trust and insufficient trust. More precisely, it is possible, unlike in approaches where only trust is accounted for, to ''weigh'' differently information from helpful, malicious, unknown, or neutral sources