The European Interoperability Reference Architecture (EIRA), is an architecture content metamodel defining the most salient architectural building blocks (ABBs) needed to build interoperable e-Government systems. The EIRA provides a common terminology that can be used by people working for public administrations in various architecture and system development tasks. The EIRA was created and is being maintained in the context of the ISA Programme. The EIRA uses (and extends) the ArchiMate language as a modelling notation and uses service orientation as an architectural style. The EIRA is aligned with the European Interoperability Framework (EIF) and complies with the context given in the European Interoperability Strategy (EIS).