This text looks at the whole process of building a business process model, capturing it 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 are powerful, easy to use and applicable for the "new world" of component-based systems and the integration of systems from dependable components. The book also presents specification, design, implementation and testing in a user-oriented fashion, using simple, formal and diagramming techniques. The first part provides a simple introduction to the method, together with a complete case study. The second part describes the mathematical theory behind the methods and claims made.