In the transactionalist model, integration has two key dimensions. The first is a process of social integration, leading to the formation of pluralistic security communities. The formation of security communities relies on the notion that international transactions—communication, migration, mutual services, military collaboration and so forth trigger the process of social-psychological learning which in turn produce common identities and trust among social actors. The second dimension is the process of political integration. Once pluralistic community formation has taken place, political elites may opt to build common supranational institutions, thereby producing ‘amalgamated’ security communities (essentially federal unions).