eGovernment is characterized by the usage of multiple applications and heterogeneous data environments. Although the outcomes of administrative processes are defined quite good, the processes themselves are different depending on geographical, political or systemic factors. A vivid example for such a diversity are the business registers (BR) of the member states of the European Union (EU). They all have in common that they are gathering and providing information about companies and related data. But not only their data processed is totally different - also the underlying processes are. The project BRITE (Business Register Interoperability Throughout Europe) aims to build interoperability between the BRs in order to facilitate EU-wide transactional services for companies to e.g. register their branch in another country. These goals willbe achieved by the application of ontology-driven semantics. This paper introduces the approach to develop a common BRITE domain ontology which links up national domain ontologies and BR processes. In this way, interoperability is reached among various national business registers and their respective services. The BRITE platform thereby serves as an intermediary to link up the diverging ontologies of national business registers.