Today the development of software in process automation is a step by step strategy along the life cycle with different notations and different tools. The requirement analysis and the basic engineering could be described and structured with project management software using natural language. The software design is mostly function oriented and component based with IEC 61131-3 development environments and implemented on different targets. There is a high demand for modeling software using the UML has been evaluated for process automation regarding a typical real time application using one of the leading UML tools (Rhapsody from iLogix).