Soft Real Time Systems Predictability Vs Efficiency

Hard real-time systems are very predictable, but not sufficiently flexible to adapt to dynamic situations. They are built under pessimistic assumptions to cope with worst-case scenarios, so they often waste resources. Soft real-time systems are built to reduce resource consumption, tolerate overloads and adapt to system changes. They are also more suited to novel applications of real-time technology, such as multimedia systems, monitoring apparatuses, telecommunication networks, mobile robotics, virtual reality, and interactive computer games. This unique monograph provides concrete methods for building flexible, predictable soft real-time systems, in order to optimize resources and reduce costs. It is an invaluable reference for developers, as well as researchers and students in Computer Science.

Paperback. This volume contains the proceedings of the 21st IFAC/IFIP Workshop on Real Time Programming (WRTP'96) held in Gramado, Brazil on 4-6 November 1996. Over the years, this series of annual workshops has become an excellent forum for exchanging information on technological advances and practices in real time computing - a field that is rapidly becoming an essential enabling discipline in computer science and engineering.The technical programme of the workshop maintained the outstanding quality of the series and covered all the latest research and developments in scheduling, operating systems, communications, timing analysis, system development, databases, formal methods and applications. In addition to high quality papers, the programme featured three world class keynote speakers and some poster presentations. These proceedings, therefore, comprise 21 full papers, three keynote addresses and five short contributions.

Abstract: "Complex real-time systems need databases to support concurrent data access and provide well-defined interfaces between software modules. However, conventional database systems and prior real-time database systems do not provide the performance or predictability needed by high-speed, hard real-time applications. To address this need, we have designed, implemented, and evaluated an object-oriented software system called MDARTS (Multiprocessor Database Architecture for Real-Time Systems). MDARTS avoids the client-server overhead of most prior real-time database systems and object-oriented real-time systems by moving transaction execution into application tasks. By eliminating these sources of overhead and focusing on basic data management services for hard real-time systems (data sharing, serializable transactions, and multiprocessor support), our MDARTS prototype provides guaranteed transaction times approximately three orders of magnitude faster than prior real-time database systems. Another contribution of MDARTS is that it supports explicit declarations of real- time requirements and semantic constraints within application code. The MDARTS library examines these declarations at database object initialization time and attempts to construct objects that are compatible with the requirements. MDARTS supports both local shared-memory transactions and remote transactions that use remote procedure calls. Except for variations in transaction time guarantees, the locations and implementations of MDARTS objects are transparent to applications. MDARTS provides a C++ interface rather than a query language interface. Our MDARTS prototype runs on VME-based multiprocessors and Sun workstations, and we have used MDARTS to implement a controller for an actual manufacturing machine."

This updated edition offers an indispensable exposition on real-time computing, with particular emphasis on predictable scheduling algorithms. It introduces the fundamental concepts of real-time computing, demonstrates the most significant results in the field, and provides the essential methodologies for designing predictable computing systems used to support time-critical control applications. Along with an in-depth guide to the available approaches for the implementation and analysis of real-time applications, this revised edition contains a close examination of recent developments in real-time systems, including limited preemptive scheduling, resource reservation techniques, overload handling algorithms, and adaptive scheduling techniques. This volume serves as a fundamental advanced-level textbook. Each chapter provides basic concepts, which are followed by algorithms, illustrated with concrete examples, figures and tables. Exercises and solutions are provided to enhance self-study, making this an excellent reference for those interested in real-time computing for designing and/or developing predictable control applications.

"Real-time Systems’ Quality of Service" examines the attainability of efficiency, economy, and ease of use, which make up the quality of service of technologically advanced products. "Real-time Systems’ Quality of Service" reviews the state of the art in quality of service evaluation for real-time systems. It gives a classification of the relevant parameters for quality of service evaluation and also determines the critical points in the design and development process of real-time systems – where performance criteria should be applied or checked. Then, software development and certification standards are assessed, and finally the authors elaborate on how the suggested criteria should be applied to the design, development, and certification process of real-time systems. "Real-time Systems’ Quality of Service" will guide researchers and postgraduates in embedded and real-time systems through the process of introducing quality of service parameters into real-time systems.