Case-based Selection Requirements Specifications for Telecommunication Systems

Using formal specifications based on varieties of mathematical logic is becoming common in the process of designing and implementing software. The advantage of this procedure is that it enables us to verify the specification's properties before the real system is implemented. Up to now, formal methods were usually applied to include all details of the final system in the specification. in large, complex systems this requires sophisticated logic, which makes theorem proving a difficult and complex task. Telecommunication systems are large and complex. However, our case-based approach uses course-grained requirements sketches to outline the basic behaviour of the system's functional components, thereby allowing us to identify, re-use and adapt requirements (from cases stored in a library) to construct new cases. By using cases that have already been tested, integrated and implemented, less effort is needed to produce requirements specifications on a large scale. Using a hypothetical telecommunication system as our example, we shall show how comparatively simple logic can be used to capture course-grained behaviour and how a case-based approach benefits from this. The input from these examples is used to induce a set of state-transition rules that are applied to match and identify the cases whose behaviour corresponds most closely to the designer's intentions.