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 "e;new world"e; 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.