It is, indeed, widely acceptable today that nowhere is it more important to focus on the improvement of software quality than in the case of systems with requirements in the areas of safety and reliability - especially for distributed, real-time and embedded systems. Thus, much research work is under progress in these fields, since software process improvement impinges directly on achieved levels of quality, and many application experiments aim to show quantitative results demonstrating the efficacy of particular approaches. Requirements for safety and reliability - like other so-called non-functional requirements for computer-based systems - are often stated in imprecise and ambiguous terms, or not at all. Specifications focus on functional and technical aspects, with issues like safety covered only implicitly, or not addressed directly because they are felt to be obvious; unfortunately what is obvious to an end user or system user is progressively less so to others, to the extend that a software developer may not even be aware that safety is an issue. Therefore, there is a growing evidence for encouraging greater understanding of safety and reliability requirements issues, right across the spectrum from end user to software developer; not just in traditional safety-critical areas (e.g. nuclear, aerospace) but also acknowledging the need for such things as heart pacemakers and other medical and robotic systems to be highly dependable.
