Science From Play-In Scenarios to Code:

A development scheme for complex reactive systems leads from a userfriendly requirements capture method, called play-in scenarios, to full behavioral descriptions of system parts, and from there to final implementation. In a 1992 Computer article, 1 I tried to present an optimistic view of the future of development methods for complex systems. Research since then only supports this optimism, as I will attempt to show. This article presents a general, rather sweeping development scheme, combining ideas that have been known for a long time with more recent ones. The scheme makes it possible to go from a high-level userfriendly requirements capture method—which I call play-in scenarios—via a rich language for describing message sequencing to a full model of the system, and from there to final implementation. A cyclic process of verifying the system against requirements and synthesizing system parts from the requirements is central to the proposal. The article puts special emphasis on the languages, methods, and computerized tools that allow smooth but rigorous transitions between the various stages of the scheme. In contrast to database systems, this article focuses on systems that have a dominant reactive, event-driven facet. For these systems, modeling and analyzing behavior is the most crucial and problematic issue. MODELING THE SYSTEM Over the years, the main approaches to high-level system modeling have been structured-analysis/structured-design (SA/SD) and object-oriented analysis and design (OOAD). The two modeling approaches are about a decade apart in initial conception and evolution. Over the years, both approaches have yielded visual formalisms for capturing the various parts of a An early version of this article appeared in Proc. Fundamenta