Integrated formal and informal specification techniques (FISTs) have been the focus of a number of research projects since the mid-eighties. Research in this area aim at producing specification techniques that integrate concepts and notations used in mature formal specification techniques (FSTs) and popular graphical modeling methods such as Structured Analysis (SA) and Object-Oriented Analysis (OOA).
In this paper we illustrate, using the results of two case studies, two roles FSTs can play in the context of less formal graphical requirements modeling and analysis techniques. In the first case study discussed an extended Petri Net model is used to prototype a textbook SART (SA/Real-Time) model. In this case, the formal model acts as a prototype, and is used to dynamically validate the requirements expressed in the SART model. In the second case study an integrated OOA method (Fusion) and FST (Z) is used to create requirements models that are graphical and analyzable. In this case, the formal models act as more precise representations of the requirements captured by the graphical models.