FernUni spezial

Duties

The chair of computer engineering based on its teaching duties in

• computer engineering,
• process automation,
• distributed process control systems, and
• safety-related real-time systems,

mainly deals in research with questions of computer-aided automation of industrial processes by so-called real-time and embedded systems. Of particular interest are their conceptual foundations, applicationoriented computer architectures, and peripheral devices with exactly predictable timing behaviour as well as real-time operating systems and real-time programming languages. In the field of highly dependable programmable electronic systems for safety-critical automation applications, which is closely related to real-time and embedded systems, fail-safe components, techniques to analyse timing behaviour, formal correctness proofs of basis software, and methods for the safety-licensing of software are developed. A recently commenced thread of research focuses on applications of chaos control and synchronisation as well as of methods of soft computing to problems of information technology.

Process Automation

Digital computers working in process automation have the task to execute programs that are associated with external technical processes. On demand of the processes, acquisition and evaluation of process data as well as suitable reactions have to be carried out punctually and keeping pace with the process dynamics. Here, priority is not given to execution speed, but to timeliness of the reactions within given and predictable bounds. Real-time systems defined this way are, thus, characterised by the fact that the functional correctness of a system is not only dependent on the results of calculations, but also on the times when these results are produced, as a consequence of which they differ fundamentally from other data processing systems. The requirement for timeliness of real-time systems is complemented by the requirement for dependability, as there is hardly a real-time system without safety relevance in practice.

Real-time Computing

Owing to the intrinsic problems of real-time operation as outlined above, the chair bases its research on working out fundamental principles, in particular with respect to the concept of time in computer science and engineering. As the temporal behaviour of presently available computing systems is predictable in exceptional cases at most, a wide and extremely important research field exists, that is being addressed by the chair. The objective of this work is the development of timing analysis techniques and of computing systems with completely predictable behaviour. Elaborating this field many aspects of conventional programming languages, compilers, operating systems, and hardware architectures are being questioned and changed. Innovative, application and programming-language-oriented real-time computer architectures are being designed which satisfy the predictability requirements and which keep the semantic gap, that has to be filled by an operating system, as small as possible. Application-specific peripheral devices with exactly defined timing behaviour are being developed as well. In the field of real-time operating systems, the chair carries through the formal correctness proof of an operating system kernel.

The chair actively participates in the further development of the German higher real-time programming language PEARL, in order to extend its technically leading position. The objectives of this research are to meet the requirement of predictable performance without any compromises and to realise a new programming paradigm: program design and design of the corresponding correctness proofs shall constitute a unity, which would mean a considerable step forward towards safety-licensing of software.

The further development of requirements engineering methods and of design tools for real-time systems focusses on providing suitable analysers and formal verification tools for each development phase. As a consequence of the predictability and reliability requirements this means a further paradigm change from empirical a posteriori verification (tests), that cannot prove the absence of errors, towards designintegrated verification with the quality of mathematical rigour.

Safety-related Real-time Systems

Safety-related real-time systems - or more precisely: highly dependable programmable electronic systems for safety-critical control and regulation applications - form a completely new field, that stands at the beginning of its treatment in research and teaching. The significance of this subject arises from the growing awareness for safety in our society on the one hand and from the technological trend towards more flexible, i.e., program-controlled, regulation and control devices on the other hand. It is the aim to reach the state that real-time systems can be constructed with a sufficient degree of confidence in their dependability that enables their licensing for safety-critical control and regulation tasks by the pertaining authorities on the basis of formal approvals. At the present state of technological development, simplicity is a basic prerequisite for that and, therefore, chosen as the pursued methodical approach.

The research activities particularly deal with methods to prove the correctness of software. The spectrum of such, more or less formal, procedures is screened, classified, and tested for their practical usability. The main focus of the subsequent activities is to make the re-use of software components easier, once they have been recognised as correct, and to prove the correctness of software systems constructed from them with the help of methods as simple and easily understandable as possible. The mentioned activities are carried out in close co-operation with the chair of data processing technology.

Chaos Control

In close co-operation with the Centre for Chaos and Complex Networks at the City University of Hong Kong, comprehensive research is carried out on the emerging and cutting-edge discipline of chaos theory, chaos control, and its applications to various areas of engineering and information technology. The fundamentally oriented part of this research includes modeling and theoretical analysis of various chaotic systems, chaos control when chaos is harmful, as well as anti-control of chaos when chaos turns out to be useful and beneficial under certain circumstances. With respect to the application domain, currently this work focuses on chaos-based cryptography exploiting the close relationship between chaos and cryptography. The fundamental features of chaos, such as ergodicity, the mixing and exactness properties, and the sensitivity to initial conditions are combined with the "confusion" and "diffusion" properties to yield good ciphers. Within this scope, methods for chaos-based image encryption, video encryption using spatial-temporal chaos, chaotic pseudo-random number generation, and for the encryption of streams of digital data are being devised and investigated.

Methods of Soft Computing

Soft computing is a collection of synergetic methodologies for flexible information processing to handle ambiguous situations in real life. Their guiding principle is to devise computational methods that can provide acceptable approximate solutions to both precisely and imprecisely formulated problems at low cost. Fuzzy sets represent a natural framework to deal with uncertainty. Neural networks are widely used to model capabilities. Genetic algorithms are an efficient search and optimisation tool. Rough sets help in granular computation and knowledge discovery. Computing with words has, in a narrow sense, the goal to develop the "arithmetics" of a computation with vague or with uncertain values, while, in a wide sense, it can be classified into reasoning with words, modeling with words, and programming with words. These methods are being applied in on-going research on web mining, the semantic web, ontologies, and search engines. Furthermore, fuzzy modeling, fuzzy control with special emphasis on chaotic systems, and anti-control of chaos in fuzzy systems are studied.

• More Information:
  • Real-time programming language PEARL [external]
  • GI-FA Echtzeitsysteme [german, external]
  • Gesellschaft für Informatik e.V. [external]

FernUniversität in Hagen, Chair of Computer Engineering, 58084 Hagen, Germany, Tel.: +49 2331 987-372