Correct Systems looks at the whole process of building a business process model, capturing that in a formal requirements statement and developing a precise specification. The issue of testing is considered throughout the process and design for test issues are fundamental to the approach. A model (language) and a methodology are presented that is very powerful, very easy to use and applicable for the "new world" of component based systems and the integration of systems from dependable components. This book discusses a new area which will be of interest to both software and hardware designers. It presents specification, design, implementation and testing in a user-oriented fashion using simple formal and diagramming techniques with a high level of user-friendliness. The first part provides a simple introduction to the method together with a complete, real case study. The second part describes, in detail, the mathematical theory behind the methods and the claims made.