Formal specification techniques as a catalyst in validation

The American Heritage Dictionary defines a catalyst as a substance, usually present in small amounts relative to the reactants, that modifies and especially increases the rate of a chemical reaction without being consumed in the process. This article reports on the experience gained in an industrial project that formal specification techniques form such a catalyst in the validation of complex systems. These formal development methods improve the validation process significantly by generating precise questions about the system's intended functionality very early and by uncovering ambiguities and faults in textual requirement documents. This project has been a cooperation between the IST and the company Frequentis. The Vienna Development Method (VDM) has been used for validating the functional requirements and the existing acceptance tests of a network node for voice communication in air traffic control. In addition to several detected requirement faults, the formal specification highlighted how additional test-cases could be derived systematically.