The need to employ formally based methods in software development, e.g., with safety critical software, is being increasingly honoured as an alternative to (conventional) software engineering since it enables, e.g., early simulation, verification and automatic test case generation. On the other hand, insights and procedures of (conventional) software engineering have stood the test in practice. Therefore, it is our goal to combine the advantages of both approaches, viz. conventional "best practices" and formal methods of software engineering, to obtain an integrated software development methodology in terms of a generally accepted science of construction. This comprises not only theoretical and methodological aspects but also tools and applications.