Expectation reasoning using regret and disappointment

A critical aspect of an agent system is the ability to deal with unexpected situations to determine an appropriate course of action in a changing environment. In this paper, we investigate the incorporation of the mental attitudes of regret and disappointment (which have been studied by economists using utility theory) into the agent's reasoning system in order to improve its ability to deal with unexpected events. Mental attitudes in agent systems have generally been expressed in modal logics, such as the Belief-Desire-Intention (BDI) logic and epistemic logic, and, more recently, in a logic of expectation and observation. We show how regret and disappointment can be naturally integrated into a framework based on the attitudes of expectation and observation, and describe some key properties of the system.