Errors within computer programs make trains collide, space shuttle launch fail, airplanes crash, and a lot of nicely manufactured products ending up as garbage. Most functions of real-time controls can ultimately only be tested and validated in a real-world environment. Regarding source code debugging and maintenance of programs, a systematical, error-free, and complete documentation is crucial, starting with the analysis and leading over the entire life-cycle of the system. The instruments used in this respect are CASE tools. The tool presented here is Process Oriented Analysis.