We use Kripke structures of autoepistemic logic to classify various semantics for disjunctive logic programs with default negation. We have observed that nonmonotonic reasoning can be characterized by Kripke structures whose beliefs are justified. We also observed that two different types of negative introspection in autoepistemic reasoning present two different interpretations of default negation: consistency-based and minimal-model-based; we further observed that all logic program semantics fall into three semantical points of view: the skeptical, stable, and partial-stable. Based on these observations, we classify disjunctive logic program semantics into six different categories, and discuss the relationships among various semantics.