Formal methods enable computer architecture and software design to be mathematically proved correct before they are implemented. The complexity and time-consuming nature of such proofs have limited the applications of formal methods in the main to defence and safety-critical applications. The mural project (a joint Alvey-funded project between "M"anchester "U"niversity and "R"utherford "A"ppleton "L"aboratories) has developed a software support system to help the user of formal methods. mural has created a user-friendly software environment (with extensive use of windows) that makes best use of human talents to produce computer systems that are proved to be correctly designed. Professor Cliff Jones is internationally known as the developer of the VDM system of formal notation (Vienna Development Method). This book describes the requirements, concepts, and realisation of the mural system. The authors present systematically and completely the results of this substantial research project, from the basic theoretical level to its effective implementation. The book will be of equal interest to academics working on formal methods at research level (and perhaps to graduate research students), and to practitioners and software engineers who are using - or who will have to use for defence contracts, etc. - formal methods.