Within the ESPRIT III project OSACA (Open System Architecture for Controls within Automation systems) of the European Commission the necessary specifications for an open control system were worked out and first prototypes of the system platform were realized. The system platform is the basis of the OSACA architecture and acts as the framework for the integration of application-oriented functionality in a control system.
Several initiatives — under them the German project HÜMNOS — are developing application modules for the OSACA architecture. This paper describes the results that have come out of the OSACA initiative so far, and explains the general structure and design of control applications for the provided framework. Special emphasis is put on the reference architecture which guarantees the interoperability between the single control-specific, vendor-neutral application modules. As illustration, the interaction of an HMI application with OSACA compliant controllers of different vendors is presented.