Book excerpt: The development of any Software (Industrial) Intensive System, e.g. critical embedded software, requires both different notations, and a strong devel- ment process. Different notations are mandatory because different aspects of the Software System have to be tackled. A strong development process is mandatory as well because without a strong organization we cannot warrantee the system will meet its requirements. Unfortunately, much more is needed! The different notations that can be used must all possess at least one property: formality. The development process must also have important properties: a exha- tive coverage of the development phases, and a set of well integrated support tools. In Computer Science it is now widely accepted that only formal notations can guarantee a perfect de?ned meaning. This becomes a more and more important issue since software systems tend to be distributed in large systems (for instance in safe public transportation systems), and in small ones (for instance numerous processors in luxury cars). Distribution increases the complexity of embedded software while safety criteria get harder to be met. On the other hand, during the past decade Software Engineering techniques have been improved a lot, and are now currently used to conduct systematic and rigorous development of large software systems. UML has become the de facto standard notation for documenting Software Engineering projects. UML is supported by many CASE tools that offer graphical means for the UML notation.