Starting as a rather simple message standard to be used within hospitals, the scope of HL7 has been extended to covering all domains and institutions in health. The most important development of the HL7 standard set was its development towards a model-based message specification methodology and the further movement towards a unified development process: HL7 Version 3. The focus was design for interoperability, which is also the driving aspect of architectural standards such as OMG's CORBA or the CEN EN 13606 Electronic Health Record Communication. The paper gives an overview about the HL7 standard set, comparing it with the principles of advanced information systems architecture.