ABSTRACT
Safety and security critical computer systems need to be developed in order to achieve an appropriate level of integrity and an corresponding operational trustworthiness within their application environment. There are two separate concerns for those developing and assessing such systems: Is the system safe or secure?; Is the system correct, where its implementation satisfies its specification? Clearly, these concerns affect both the development and the assessment of such critical system, in terms of both technical and management methods. The role of software within such critical systems is assuming significant responsibility, in addition to often being regarded as the weak link of the system. This paper addresses the problem of developing critical software systems anticipating the need for rigourous, possibly third party, system assessments.
