From a technological viewpoint, the actual evolution of the fieldbus systems (its timeline is shown in Fig. 2) was heavily influenced by the development of computer networks,
the key contribution undoubtedly being the International Organization for Standardization (ISO)/Open Systems Interconnection (OSI) model. This reference model was (and still is) the starting point for the development of many complex communication protocols. The first application of the OSI model to the domain of automation was the definition of the Manufacturing Automation
Protocol (MAP) in the wake of the CIM idea [7].