Editorial: Hybrid Systems

Abstract

Embedded software, where programs are interacting with a physical environment through electro-mechanical sensors and actuators, has traditionally been considered a strange corner of computer science, perhaps even an area belonging more to the control engineers. However, with inexpensive and powerful technology there is a tremendous increase in the number of applications, and concurrently a rise in the complexity, because it is feasible to make advanced intelligent control of the physical systems. Yet, if these systems are to be safe to use, they require integrated design procedures based on sound models of the intricate interaction between programs and the environment which is typically modelled as a dynamical system specified by differential equations. The combined theory is known as Hybrid Systems and has been investigated intensely since the 1990s by both computer scientists and control engineers. Today there is a body of results on the modelling, analysis, and synthesis of such systems. In analysis, a major inspiration has been the advances in symbolic model checking, and in the even harder problem of synthesis, techniques based on bisimulation and game theories link up to concurrency theory. This special issue aims to illustrate some results of the interdisciplinary research within the Hybrid Systems, and in particular to show the breadth of the field and the opportunities for further interaction between control theory and computer science. The initiative was taken within the IFIP Working Group 2.2 on “Formal Description of Programming Concepts”. This is one of the first Working Groups, created about 40 years ago, and it is dedicated to explain programming concepts through the development, examination and comparison of formal models for such concepts. Since the embedded software systems area is growing rapidly, the Working Group takes an