Agent-oriented epistemic reasoning: Subjective conditions of knowledge and belief

This paper introduces a formal system Sigma of subjective epistemic reasoning that encodes a method of reasoning with conditions of knowledge and belief. The conditions are subjective in that they are taken from the perspective of an agent's perception of his own state of knowledge or belief with respect to his observable world. Belief is measured along a series of linguistic degrees, e.g., strongly believes, fairly confidently believes, somewhat disbelieves, etc., and knowledge is taken as unequivocal belief. The system employs a novel, dual-leveled language that follows fuzzy logic by interpreting the logical or and and as the arithmetical max and min. Numerous properties of Sigma, illustrating its intuitive appeal for the intended purpose, are derived. (C) 2003 Elsevier B.V. All rights reserved.