Experience of implementation from a formal specification

The paper is concerned with the practical realities of using formal specifications in the implementation of complex systems, such as C3MIS, with the objective of ensuring safety or security. It first considers the question of what is meant by a formal specification, why formal specifications are increasingly being demanded in defence systems and why there appears to be a problem with achieving the objectives set for their use. The problems are discussed in more detail, with reference to a particular implementation project, although details have been simplified and modified for pedagogical and security reasons. Finally, the paper discusses what, in the author´s view, is and is not practicable to expect from formal specifications in the near to medium term