Theoretical approaches to international organizations are classified under two main categories: Traditional Approaches to International Organizations and Revisionist Approaches to International Organizations. Traditional approaches include Realism and Liberalism. They have a state-centric approach to the analysis of international organizations. For them, states are both principal actors of international system and also rational actors making cost-benefit analysis of every alternative and select the ones that maximize their benefits. Revisionist approaches, including Functionalism, Neo-functionalism and Transactionalism go beyond the state-centric approach and examine international organizations as significant actors beside states. These are mostly known as international integration theories.