PrefaceIn 1995, the Deutsche Forschungsgemeinschaft (DFG), the largest public research funding organization in Germany, decided to launch a priority program (Schwerpunktprogramm in German) called Kondisk-Dynamics and Control of Systems with Mixed Continuous and Discrete Dynamics. Such a priority program is usually sponsored for six years and supports about twenty scientists at a time, in engineering and computer science mostly young researchers working for a doctoral degree. There is a yearly competition across all disciplines of arts and sciences for the funding of such programs, and the group of proposers was the happy winner of a slot in that year. The program started in 1996 after an open call for proposals; the successful projects were presented and re-evaluated periodically, and new projects could be submitted simultaneously. During the course of the focused research program, 25 different projects were funded in 19 participating university institutes, some of the projects were collaborative efforts of two groups with different backgrounds, mostly one from engineering and one from computer science.There were two main motivations for establishing Kondisk. The first was the fact that technical systems nowadays are composed of physical components with (mostly) continuous dynamics and computerized control systems where the reaction to discrete events plays a major role, implemented in Programmable Logic Controllers (PLCs), Distributed Control Systems (DCSs) or real-time computer systems. These two elements interact closely, and the resulting behavior can be surprisingly complex even for very simple systems, as demonstrated for the filling of three or more tanks by a switched server (Chase et al., 1993. Such complex behavior can neither be analyzed nor synthesized by methods that are based on either purely continuous or purely discrete systems theory. Despite the lack of theoretical tools or even powerful simulation environments for systems with mixed continuous and discrete dynamics, such systems have been engineered successfully on a trial-and-error basis, applying a combination of "divide and conquer" and "separation of concerns". The price that has to be paid, however, is extensive testing, frequent iterations in the design process, and the lack of guarantees for safety and performance properties.The second important factor in the creation of the priority program Kondiskwas the growing awareness of the need for a more comprehensive approach to hybrid systems both in the computer science and the control engineering communities, and the fact that important foundations had been laid in both camps -and sometimes across their borders as well. It was one of the key ideas in the call for proposals that the interaction of scientists from computer science and control engineering should be stimulated, and this resulted in several interdisciplinary projects. These projects not only led to interesting and novel results but generally created a deeper understanding of the complementary theories and issues on both sides. So...
