 It should be noted that the two approaches are not equivalent. Consider the following doxastic model (from Halpern, Samet, &amp; Segev 2009a), with the serial, transitive and Euclidean doxastic relation \(R_B\) represented by dashed arrows, and its derived reflexive, transitive and symmetric (i.e., equivalence) epistemic relation \(R_K\) represented by solid ones.