2 A Formal Methods Case Study : Using \ light - weight " VDM for the Developmentof a Security System

This paper describes a formal methods case study in which one module of an existing security system was redeveloped using the \light-weight" Vienna Development Method supported by the IFAD Toolbox. The result is compared with the existing version in terms of eeort and quality. In this project, formal methods { even in its \light-weight" form { have increased software quality while the development eeorts were comparable. The second part of the paper contains a discussion of the relevance of these results from the point of view of the team that has used conventional methods for the development of the original version.